Instructions for using the php in_array function and instructions for what you need to pay attention to in_array

in_array
(PHP 4, PHP 5)

in_array — Check whether a certain value exists in the array

Description

bool in_array ( mixed $needle , array $haystack [, bool $strict ] )

Search for needle in haystack, if found, return TRUE, otherwise return FALSE.

If the value of the third parameter strict is TRUE, the in_array() function will also check whether the type of needle is the same as that in haystack.

Note: If needle is a string, the comparison is case-sensitive.

Note: Before PHP version 4.2.0, needle was not allowed to be an array.

Example #1 in_array() example

<?php 
$os = array("Mac", "NT", "Irix", "Linux"); 
if (in_array("Irix", $os)) { 
echo "Got Irix"; 
} 
if (in_array("mac", $os)) { 
echo "Got mac"; 
} 
?>

The second condition fails because in_array() is case-sensitive, so the above program is displayed as:
Got Irix

Example #2 in_array() Strict type checking example

<?php 
$a = array(&#39;1.10&#39;, 12.4, 1.13); 

if (in_array(&#39;12.4&#39;, $a, true)) { 
echo "&#39;12.4&#39; found with strict check\n"; 
} 
if (in_array(1.13, $a, true)) { 
echo "1.13 found with strict check\n"; 
} 
?>

The above example will output:

1.13 found with strict check

Example #3 in_array() using array as needle

<?php 
$a = array(array(&#39;p&#39;, &#39;h&#39;), array(&#39;p&#39;, &#39;r&#39;), &#39;o&#39;); 

if (in_array(array(&#39;p&#39;, &#39;h&#39;), $a)) { 
echo "&#39;ph&#39; was found\n"; 
} 
if (in_array(array(&#39;f&#39;, &#39;i&#39;), $a)) { 
echo "&#39;fi&#39; was found\n"; 
} 
if (in_array(&#39;o&#39;, $a)) { 
echo "&#39;o&#39; was found\n"; 
} 
?>

The above example will output:

'ph' was found
'o' was found

Things to note:

If:

First declare an array as:

　$arr = array(*);

Then:

in_array(0, $arr) == true

It’s puzzling! {Weak language}

Solution:
in_array(strval(0), $arr, true))

For more php in_array function usage instructions and in_array notes, please pay attention to PHP Chinese for related articles net!