The array_flip() function in PHP is used to swap the values of an array with the keys. Take the following array.
$array = array('key1'=>'value1', 'key2'=>'value2');To exchange all the values with the keys we pass it through the array_flip() function.
$array = array_flip($array);
echo '<pre>'.print_r($array, true).'</pre>';This prints out the following:
Array
(
[value1] => key1
[value2] => key2
)If any of the values are the same then the highest key is overwritten. The following array:
$array = array('a', 'a', 'a', 'b');Will produce the following array when passed through array_flip().
Array
(
[a] => 2
[b] => 3
)If this bit of code is essential to the running of your program you can make sure that it exists by using the function_exists() function. This function takes a single parameter, which is the name of the function you are testing for as a string. The following code checks to see if the array_flip() function exists, and if not defines a version that works in the same way.
if (!function_exists('array_flip')) {
function array_flip($array){
$values = array();
while ( list($key, $val) = each($array) ) {
$values[$val] = $key;
}
return $values;
}
}The array_flip() function was included in PHP version 4, so you only need to do this if you expect someone to try and run your code on a very old version of PHP. However, there are many new functions included with PHP 5 that you might want to check for when writing code.