blocks|key|4086142|text|这应该能起到作用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4086143|$value+=++isset($items['four']['a'])+?+$items['four']['a']+:+99;|code-block|syntax|javascript|4086144|如果你必须大量编写这些代码，那么辅助函数将非常有用：|4086145|function+arr_get($array,+$key,+$default+=+null){
++++return+isset($array[$key])+?+$array[$key]+:+$default;
}|4086146|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

This should do the trick:

<pre><code>$value = isset($items['four']['a']) ? $items['four']['a'] : 99;
</code></pre>

A helper function would be useful, if you have to write these a lot:

<pre><code>function arr_get($array, $key, $default = null){
 return isset($array[$key]) ? $array[$key] : $default;
}
</code></pre>

blocks|key|5504081|text|就我所知没有。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5504082|您必须单独与isset进行核对|offset|length|style|CODE|5504083|echo+isset($items['four']['a'])+?+$items['four']['a']+:+99;|code-block|syntax|javascript|5504084|entityMap^0|0|6|5|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@$D|Q|E|R|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|S|8|@]|9|@]|A|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Not that I know of.

You'd have to check separately with <code>isset</code>

<pre><code>echo isset($items['four']['a']) ? $items['four']['a'] : 99;
</code></pre>

blocks|key|1975760|text|我不知道有什么方法可以精确地使用您提供的代码，但是您可以使用一个函数来解决这个问题，该函数可以接受任意数量的参数，并返回您正在寻找的参数或默认值。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1975761|用法：|1975762|echo+arr_value($items,+'four',+'a');|code-block|syntax|javascript|1975763|或者：|1975764|echo+arr_value($items,+'four',+'a',+'1',+'5');|1975765|功能：|1975766|function+arr_value($arr,+$dimension1,+$dimension2,+...)
{
++++$default_value+=+99;
++++if+(func_num_args()+>+1)
++++{
++++++++$output+=+$arr;
++++++++$args+=+func_gets_args();
++++++++for($i+=+1;+$i+<+func_num_args();+$i%2B%2B)
++++++++{
++++++++++++$outout+=+isset($output[$args[$i]])+?+$output[$args[$i]]+:+$default_value;
++++++++}
++++}
++++else
++++{
++++++++return+$default_value;
++++}

++++return+$output;
}|1975767|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

I don't know of a way to do it precisely with the code you provided, but you could work around it with a function that accepts any number of arguments and returns the parameter you're looking for or the default.

Usage:

<pre><code>echo arr_value($items, 'four', 'a');
</code></pre>

or:

<pre><code>echo arr_value($items, 'four', 'a', '1', '5');
</code></pre>

Function:

<pre><code>function arr_value($arr, $dimension1, $dimension2, ...)
{
 $default_value = 99;
 if (func_num_args() &gt; 1)
 {
 $output = $arr;
 $args = func_gets_args();
 for($i = 1; $i &lt; func_num_args(); $i++)
 {
 $outout = isset($output[$args[$i]]) ? $output[$args[$i]] : $default_value;
 }
 }
 else
 {
 return $default_value;
 }

 return $output;
}
</code></pre>

blocks|key|1608471|text|我知道这是一个老生常谈的问题，但是我在谷歌上搜索"php“就找到了这个问题，我想我应该把我想要的解决方案贴出来，可能会对其他人有所帮助。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1608472|我想要一个具有默认选项值的数组，这些值可以被自定义值覆盖。我最终使用了array_merge。|offset|length|1608473|示例：|1608474|<?php
++++$defaultOptions+=+array("color"+=>+"red",+"size"+=>+5,+"text"+=>+"Default+text");
++++$customOptions+=+array("color"+=>+"blue",+"text"+=>+"Custom+text");
++++$options+=+array_merge($defaultOptions,+$customOptions);
++++print_r($options);
?>|code-block|syntax|javascript|1608475|输出：|1608476|Array
(
++++[color]+=>+blue
++++[size]+=>+5
++++[text]+=>+Custom+text
)|1608477|entityMap|0|LINK|mutability|MUTABLE|url|http://php.net/manual/en/function.array-merge.php^0|0|Z|B|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@]|9|@$D|10|E|11|1|12]]|A|$]]|$1|F|3|G|5|6|7|13|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|14|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|15|8|@]|9|@]|A|$]]|$1|O|3|P|5|J|7|16|8|@]|9|@]|A|$K|L]]|$1|Q|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]]]

I know this is an old question, but my Google search for "php array default values" took me here, and I thought I would post the solution I was looking for, chances are it might help someone else.

I wanted an array with default option values that could be overridden by custom values. I ended up using <a href="http://php.net/manual/en/function.array-merge.php">array_merge</a>.

Example:

<pre><code>&lt;?php
 $defaultOptions = array("color" =&gt; "red", "size" =&gt; 5, "text" =&gt; "Default text");
 $customOptions = array("color" =&gt; "blue", "text" =&gt; "Custom text");
 $options = array_merge($defaultOptions, $customOptions);
 print_r($options);
?&gt;
</code></pre>

Outputs:

<pre><code>Array
(
 [color] =&gt; blue
 [size] =&gt; 5
 [text] =&gt; Custom text
)
</code></pre>

blocks|key|1975916|text|从PHP7.0开始您可以使用null合并运算符??|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|CODE|entityRanges|data|1975917|$value+=+$items['one']['two']+??+'defaut';|code-block|syntax|javascript|1975918|用于低于5.6的|1975919|你也可以这样做：|1975920|$value+=++$items['four']['a']+?:+99;|1975921|这等同于：|1975922|$value+=++$items['four']['a']+?+$items['four']['a']+:+99;|1975923|它省去了将整个语句包装到一个函数中的需要！|1975924|请注意，当且仅当未在items['four']中设置密钥'a'时，此函数才不会返回99。相反，当且仅当值$items['four']['a']为false+(未设置或为false值，如0)时，它才返回99。|1975925|entityMap^0|0|9|N|2|0|0|0|0|8|0|0|0|5|0|0|0|L|0|0|2V|A|D|S|3|1G|J|0^^$0|@$1|2|3|4|5|6|7|11|8|@$9|12|A|13|B|C]|$9|14|A|15|B|D]]|E|@]|F|$]]|$1|G|3|H|5|I|7|16|8|@]|E|@]|F|$J|K]]|$1|L|3|M|5|6|7|17|8|@]|E|@]|F|$]]|$1|N|3|O|5|6|7|18|8|@$9|19|A|1A|B|C]]|E|@]|F|$]]|$1|P|3|Q|5|I|7|1B|8|@]|E|@]|F|$J|K]]|$1|R|3|S|5|6|7|1C|8|@$9|1D|A|1E|B|C]]|E|@]|F|$]]|$1|T|3|U|5|I|7|1F|8|@]|E|@]|F|$J|K]]|$1|V|3|W|5|6|7|1G|8|@$9|1H|A|1I|B|C]]|E|@]|F|$]]|$1|X|3|Y|5|6|7|1J|8|@$9|1K|A|1L|B|C]|$9|1M|A|1N|B|D]|$9|1O|A|1P|B|D]|$9|1Q|A|1R|B|D]]|E|@]|F|$]]|$1|Z|3|-4|5|6|7|1S|8|@]|E|@]|F|$]]]|10|$]]

As of PHP7.0 you can use the null coalescing operator <code>??</code>

<pre><code>$value = $items['one']['two'] ?? 'defaut';
</code></pre>

For &lt;5.6

You could also do this:

<pre><code>$value = $items['four']['a'] ?: 99;
</code></pre>

This equates to:

<pre><code>$value = $items['four']['a'] ? $items['four']['a'] : 99;
</code></pre>

It saves the need to wrap the whole statement into a function!

Note that this does not return 99 if and only if the key <code>'a'</code> is not set in <code>items['four']</code>. Instead, it returns 99 if and only if the value <code>$items['four']['a']</code> is false (either unset or a false value like 0).

blocks|key|1975945|text|使用Array_Fill()函数|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1975946|http://php.net/manual/en/function.array-fill.php|offset|length|1975947|$default+=+array(
++++++++++++++'a'+=>+1,
++++++++++++++'b'+=>+2,
++++++++++++++'c'+=>+3,
++++++++++++++'d'+=>+4,
+++++++++);
$arr+=+Array_Fill(1,3,$default);
print_r($arr);|code-block|syntax|javascript|1975948|这就是结果：|1975949|Array
(
++++[1]+=>+Array
++++++++(
++++++++++++[a]+=>+1
++++++++++++[b]+=>+2
++++++++++++[c]+=>+3
++++++++++++[d]+=>+4
++++++++)

++++[2]+=>+Array
++++++++(
++++++++++++[a]+=>+1
++++++++++++[b]+=>+2
++++++++++++[c]+=>+3
++++++++++++[d]+=>+4
++++++++)

++++[3]+=>+Array
++++++++(
++++++++++++[a]+=>+1
++++++++++++[b]+=>+2
++++++++++++[c]+=>+3
++++++++++++[d]+=>+4
++++++++)

)|1975950|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|1C|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|W|8|@]|9|@$D|X|E|Y|1|Z]]|A|$]]|$1|F|3|G|5|H|7|10|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|11|8|@]|9|@]|A|$]]|$1|M|3|N|5|H|7|12|8|@]|9|@]|A|$I|J]]|$1|O|3|-4|5|6|7|13|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|C]]]]

Use Array_Fill() function

<a href="http://php.net/manual/en/function.array-fill.php" rel="nofollow">http://php.net/manual/en/function.array-fill.php</a>

<pre><code>$default = array(
 'a' =&gt; 1,
 'b' =&gt; 2,
 'c' =&gt; 3,
 'd' =&gt; 4,
 );
$arr = Array_Fill(1,3,$default);
print_r($arr);
</code></pre>

This is the result:

<pre><code>Array
(
 [1] =&gt; Array
 (
 [a] =&gt; 1
 [b] =&gt; 2
 [c] =&gt; 3
 [d] =&gt; 4
 )

 [2] =&gt; Array
 (
 [a] =&gt; 1
 [b] =&gt; 2
 [c] =&gt; 3
 [d] =&gt; 4
 )

 [3] =&gt; Array
 (
 [a] =&gt; 1
 [b] =&gt; 2
 [c] =&gt; 3
 [d] =&gt; 4
 )

)
</code></pre>

blocks|key|1976010|text|您可以从Non-standard+PHP+library使用DefaultArray。您可以从您的项目创建新的DefaultArray：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1976011|use+function+\nspl\ds\defaultarray;
$items+=+defaultarray(function()+{+return+defaultarray(99);+},+$items);|code-block|syntax|javascript|1976012|或者从items()函数返回DefaultArray：|style|CODE|1976013|function+items()+{
++++return+defaultarray(function()+{+return+defaultarray(99);+},+array(
++++++++'one'+=>+array(
++++++++++++++'a'+=>+1,
++++++++++++++'b'+=>+2,
++++++++++++++'c'+=>+3,
++++++++++++++'d'+=>+4,
+++++++++),
+++++++++'two'+=>+array(
++++++++++++++'a'+=>+1,
++++++++++++++'b'+=>+2,
++++++++++++++'c'+=>+3,
++++++++++++++'d'+=>+4,
+++++++++),
+++++++++'three'+=>+array(
++++++++++++++'a'+=>+1,
++++++++++++++'b'+=>+2,
++++++++++++++'c'+=>+3,
++++++++++++++'d'+=>+4,
+++++++++),
++++));
}|1976014|请注意，我们使用匿名函数function()+{+return+defaultarray(99);+}创建嵌套的默认数组。否则，默认数组对象的相同实例将在所有父数组字段之间共享。|1976015|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/ihor/Nspl|1|https://github.com/ihor/Nspl#defaultarray^0|4|O|0|U|C|1|0|0|3|7|0|0|C|13|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]|$A|14|B|15|1|16]]|C|$]]|$1|D|3|E|5|F|7|17|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|18|8|@$A|19|B|1A|K|L]]|9|@]|C|$]]|$1|M|3|N|5|F|7|1B|8|@]|9|@]|C|$G|H]]|$1|O|3|P|5|6|7|1C|8|@$A|1D|B|1E|K|L]]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|1F|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]|Y|$5|T|U|V|C|$W|Z]]]]

You can use <a href="https://github.com/ihor/Nspl#defaultarray" rel="nofollow">DefaultArray</a> from <a href="https://github.com/ihor/Nspl" rel="nofollow">Non-standard PHP library</a>. You can create new DefaultArray from your items:

<pre><code>use function \nspl\ds\defaultarray;
$items = defaultarray(function() { return defaultarray(99); }, $items);
</code></pre>

Or return DefaultArray from the <code>items()</code> function:

<pre><code>function items() {
 return defaultarray(function() { return defaultarray(99); }, array(
 'one' =&gt; array(
 'a' =&gt; 1,
 'b' =&gt; 2,
 'c' =&gt; 3,
 'd' =&gt; 4,
 ),
 'two' =&gt; array(
 'a' =&gt; 1,
 'b' =&gt; 2,
 'c' =&gt; 3,
 'd' =&gt; 4,
 ),
 'three' =&gt; array(
 'a' =&gt; 1,
 'b' =&gt; 2,
 'c' =&gt; 3,
 'd' =&gt; 4,
 ),
 ));
}
</code></pre>

Note that we create nested default array with an anonymous function <code>function() { return defaultarray(99); }</code>. Otherwise, the same instance of default array object will be shared across all parent array fields.

blocks|key|1608564|text|这个问题很老了，但也许我的解决方案仍然有帮助。对于我经常需要"if+array_key_exists“的项目，比如Json解析，我开发了以下函数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1608565|function+getArrayVal($arr,+$path=null,+$default=null)+{
++++if(is_null($path))+return+$arr;
++++$t=&$arr;
++++foreach(explode('/',+trim($path,'/'))+As+$p)+{
++++++++if(!array_key_exists($p,$t))+return+$default;
++++++++$t=&$t[$p];
++++}
++++return+$t;
}|code-block|syntax|javascript|1608566|然后您可以简单地“查询”数组，如下所示：|1608567|$res+=+getArrayVal($myArray,'companies/128/address/street');|1608568|这比同等的老式方式更容易阅读。|1608569|$res+=+(isset($myArray['companies'][128]['address']['street'])+?+$myArray['companies'][128]['address']['street']+:+null);|1608570|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

The question is very old, but maybe my solution is still helpful. For projects where I need "if array_key_exists" very often, such as Json parsing, I have developed the following function:

<pre><code>function getArrayVal($arr, $path=null, $default=null) {
 if(is_null($path)) return $arr;
 $t=&amp;$arr;
 foreach(explode('/', trim($path,'/')) As $p) {
 if(!array_key_exists($p,$t)) return $default;
 $t=&amp;$t[$p];
 }
 return $t;
}
</code></pre>

You can then simply "query" the array like: 

<pre><code>$res = getArrayVal($myArray,'companies/128/address/street');
</code></pre>

This is easier to read than the equivalent old fashioned way...

<pre><code>$res = (isset($myArray['companies'][128]['address']['street']) ? $myArray['companies'][128]['address']['street'] : null);
</code></pre>

blocks|key|5504432|text|在PHP7中，有一个专门为这些情况设计的新操作符，称为Null+Coalesce+Operator。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|5504433|所以现在你可以这样做：|5504434|echo+$items['four']['a']+??+99;|code-block|syntax|javascript|5504435|而不是|5504436|echo+isset($items['four']['a'])+?+$items['four']['a']+:+99;|5504437|在PHP7之前，还有另一种方法可以做到这一点：|5504438|function+get(&$value,+$default+=+null)
{
++++return+isset($value)+?+$value+:+$default;
}|5504439|下面的代码将正常工作，不会出现问题：|5504440|echo+get($item['four']['a'],+99);
echo+get($item['five'],+['a'+=>+1]);|5504441|但请注意，使用这种方式，在非数组值上调用数组属性将抛出错误。例如。|5504442|echo+get($item['one']['a']['b'],+99);
//+Throws:+PHP+warning:++Cannot+use+a+scalar+value+as+an+array+on+line+1|5504443|此外，在某些情况下会抛出致命错误：|5504444|$a+=+"a";
echo+get($a[0],+"b");
//+Throws:+PHP+Fatal+error:++Only+variables+can+be+passed+by+reference|5504445|最后，有一个丑陋的变通方法，但几乎工作得很好(在某些情况下，如下所述的问题)：|5504446|function+get($value,+$default+=+null)
{
++++return+isset($value)+?+$value+:+$default;
}
$a+=+[
++++'a'+=>+'b',
++++'b'+=>+2
];
echo+get(@$a['a'],+'c');++++++//+prints+'c'++--+OK
echo+get(@$a['c'],+'d');++++++//+prints+'d'++--+OK
echo+get(@$a['a'][0],+'c');+++//+prints+'b'++--+OK+(but+also+maybe+wrong+-+it+depends)
echo+get(@$a['a'][1],+'c');+++//+prints+NULL+--+NOT+OK
echo+get(@$a['a']['f'],+'c');+//+prints+'b'++--+NOT+OK
echo+get(@$a['c'],+'d');++++++//+prints+'d'++--+OK
echo+get(@$a['c']['a'],+'d');+//+prints+'d'++--+OK
echo+get(@$a['b'][0],+'c');+++//+prints+'c'++--+OK
echo+get(@$a['b']['f'],+'c');+//+prints+'c'++--+OK
echo+get(@$b,+'c');+++++++++++//+prints+'c'++--+OK|5504447|entityMap|0|LINK|mutability|MUTABLE|url|https://wiki.php.net/rfc/isset_ternary^0|R|M|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1G|8|@]|9|@$A|1H|B|1I|1|1J]]|C|$]]|$1|D|3|E|5|6|7|1K|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|1L|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|1M|8|@]|9|@]|C|$]]|$1|M|3|N|5|H|7|1N|8|@]|9|@]|C|$I|J]]|$1|O|3|P|5|6|7|1O|8|@]|9|@]|C|$]]|$1|Q|3|R|5|H|7|1P|8|@]|9|@]|C|$I|J]]|$1|S|3|T|5|6|7|1Q|8|@]|9|@]|C|$]]|$1|U|3|V|5|H|7|1R|8|@]|9|@]|C|$I|J]]|$1|W|3|X|5|6|7|1S|8|@]|9|@]|C|$]]|$1|Y|3|Z|5|H|7|1T|8|@]|9|@]|C|$I|J]]|$1|10|3|11|5|6|7|1U|8|@]|9|@]|C|$]]|$1|12|3|13|5|H|7|1V|8|@]|9|@]|C|$I|J]]|$1|14|3|15|5|6|7|1W|8|@]|9|@]|C|$]]|$1|16|3|17|5|H|7|1X|8|@]|9|@]|C|$I|J]]|$1|18|3|-4|5|6|7|1Y|8|@]|9|@]|C|$]]]|19|$1A|$5|1B|1C|1D|C|$1E|1F]]]]

As of PHP 7, there is a new operator specifically designed for these cases, called <a href="https://wiki.php.net/rfc/isset_ternary" rel="noreferrer">Null Coalesce Operator</a>.

So now you can do:

<pre><code>echo $items['four']['a'] ?? 99;
</code></pre>

instead of

<pre><code>echo isset($items['four']['a']) ? $items['four']['a'] : 99;
</code></pre>

There is another way to do this prior the PHP 7:

<pre><code>function get(&amp;$value, $default = null)
{
 return isset($value) ? $value : $default;
}
</code></pre>

And the following will work without an issue:

<pre><code>echo get($item['four']['a'], 99);
echo get($item['five'], ['a' =&gt; 1]);
</code></pre>

But note, that using this way, calling an array property on a non-array value, will throw an error. E.g.

<pre><code>echo get($item['one']['a']['b'], 99);
// Throws: PHP warning: Cannot use a scalar value as an array on line 1
</code></pre>

Also, there is a case where a fatal error will be thrown:

<pre><code>$a = "a";
echo get($a[0], "b");
// Throws: PHP Fatal error: Only variables can be passed by reference
</code></pre>

At final, there is an ugly workaround, but works almost well (issues in some cases as described below):

<pre><code>function get($value, $default = null)
{
 return isset($value) ? $value : $default;
}
$a = [
 'a' =&gt; 'b',
 'b' =&gt; 2
];
echo get(@$a['a'], 'c'); // prints 'c' -- OK
echo get(@$a['c'], 'd'); // prints 'd' -- OK
echo get(@$a['a'][0], 'c'); // prints 'b' -- OK (but also maybe wrong - it depends)
echo get(@$a['a'][1], 'c'); // prints NULL -- NOT OK
echo get(@$a['a']['f'], 'c'); // prints 'b' -- NOT OK
echo get(@$a['c'], 'd'); // prints 'd' -- OK
echo get(@$a['c']['a'], 'd'); // prints 'd' -- OK
echo get(@$a['b'][0], 'c'); // prints 'c' -- OK
echo get(@$a['b']['f'], 'c'); // prints 'c' -- OK
echo get(@$b, 'c'); // prints 'c' -- OK
</code></pre>

blocks|key|5504516|text|正如Slavik提到的，在PHP7中，您可以使用null合并操作符：??|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|5504517|链接到PHP+docs。|5504518|entityMap|0|LINK|mutability|MUTABLE|url|http://php.net/manual/en/language.operators.comparison.php#language.operators.comparison.coalesce^0|Y|2|0|3|8|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@]|D|@$9|T|A|U|1|V]]|E|$]]|$1|H|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]]]

In PHP7, as Slavik mentioned, you can use the null coalescing operator: <code>??</code>

Link to the <a href="http://php.net/manual/en/language.operators.comparison.php#language.operators.comparison.coalesce" rel="nofollow noreferrer">PHP docs</a>.

blocks|key|4086561|text|当前使用的是php+7.2|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4086562|>>>+$a+=+["cat_name"=>"Beverage",+"details"=>"coca+cola"];
=>+[
+++++"cat_name"+=>+"Beverage",
+++++"details"+=>+"coca+cola",
+++]
>>>+$a['price']
PHP+Notice:++Undefined+index:+price+in+Psy+Shell+code+on+line+1
=>+null
>>>+$a['price']+??+null+?+"It+has+price+key"+:+"It+does+not+have+price+key"
=>+"It+does+not+have+price+key"|code-block|syntax|javascript|4086563|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Currently using of php 7.2

<pre><code>&gt;&gt;&gt; $a = ["cat_name"=&gt;"Beverage", "details"=&gt;"coca cola"];
=&gt; [
 "cat_name" =&gt; "Beverage",
 "details" =&gt; "coca cola",
 ]
&gt;&gt;&gt; $a['price']
PHP Notice: Undefined index: price in Psy Shell code on line 1
=&gt; null
&gt;&gt;&gt; $a['price'] ?? null ? "It has price key" : "It does not have price key"
=&gt; "It does not have price key"
</code></pre>

If I have an array full of information, is there any way I can a default for values to be returned if the key doesn't exist?

<pre><code>function items() {
 return array(
 'one' =&gt; array(
 'a' =&gt; 1,
 'b' =&gt; 2,
 'c' =&gt; 3,
 'd' =&gt; 4,
 ),
 'two' =&gt; array(
 'a' =&gt; 1,
 'b' =&gt; 2,
 'c' =&gt; 3,
 'd' =&gt; 4,
 ),
 'three' =&gt; array(
 'a' =&gt; 1,
 'b' =&gt; 2,
 'c' =&gt; 3,
 'd' =&gt; 4,
 ),
 );
}
</code></pre>

And in my code

<pre><code>$items = items();
echo $items['one']['a']; // 1
</code></pre>

But can I have a default value to be returned if I give a key that doesn't exist like,

<pre><code>$items = items();
echo $items['four']['a']; // DOESN'T EXIST RETURN DEFAULT OF 99
</code></pre>

Default array values if key doesn't exist?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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如果我有一个充满信息的数组，有没有办法在键不存在的情况下设置返回值的默认值？function items() {    return array(        'one' => array(              'a' => 1,              'b' => 2,              'c' ...

问如果key不存在，是否默认数组值？
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问如果key不存在，是否默认数组值？EN