php数组中查找某个值是否存在(in_array(),array_search(),array_key_exists())
php在数组中查找指定值是否存在的方法有很多,记得很久以前我一直都是傻傻的用foreach循环来查找的,下面我主要分享一下用php内置的三个数组函数来查找指定值是否存在于数组中,这三个数组分别是 in_array(),array_search(),array_key_exists()。
首先分别介绍一下各自的定义与作用
in_array(value,array,type)
该函数的作用是在数组array中搜索指定的value值,type是可选参数,如果设置该参数为 true ,则检查搜索的数据与数组的值的类型是否相同,即恒等于。示例:
<p><?php</p>$people = array("Peter", "Joe", "Glenn", "Cleveland");<br />if(in_array("Glenn",$people)){<br /> echo "Match found";<br />}else{<br /> echo "Match not found";<br />}<br /><p>?></p>
输出:
Match found
array_key_exists(key,array)
该函数是判断某个数组array中是否存在指定的 key,如果该 key 存在,则返回 true,否则返回 false。示例:
<p><?php</p>$a=array("a"=>"Dog","b"=>"Cat");<br />if(array_key_exists("a",$a)){<br /> echo "Key exists!";<br />}else{<br /> echo "Key does not exist!";<br />}<br /><p>?></p>
输出:
Key exists!
array_search(value,array,strict)array_search()
函数与 in_array() 一样,在数组中查找一个键值。如果找到了该值,则返回匹配该元素所对应的键名。
如果没找到,则返回 false。
注意在 PHP 4.2.0 之前,函数在失败时返回 null 而不是 false。同样如果第三个参数 strict 被指定为 true,则只有在数据类型和值都一致时才返回相应元素的键名。
示例:
<p><?php</p>$a=array("a"=>"Dog","b"=>"Cat","c"=>5,"d"=>"5");<br />echo array_search("Dog",$a);<br />echo array_search("5",$a);<br /><p>?></p>
输出:ad经过实际性能对比,在数据量不大的时候,比如小于1000,查找用哪一种都行,都不会成为性能上的瓶颈。但当数据量比较大的时候,用 array_key_exists 比较合适。
据测试 array_key_exist 要比 in_array 效率高十几甚至几十倍。

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