search and replace value in PHP array

If performance is an issue, one may consider not to create multiple functions within array_map(). Note that isset() is extremely fast, and this solutions does not call any other functions at all.

$replacements = array(
    'search1' => 'replace1',
    'search2' => 'replace2',
    'search3' => 'replace3'
);
foreach ($a as $key => $value) {
    if (isset($replacements[$value])) {
        $a[$key] = $replacements[$value];
    }
}

While there isn't one function equivalent to the sample code, you can use array_keys (with the optional search value parameter), array_fill and array_replace to achieve the same thing:

EDIT by Tomas: the code was not working, corrected it:

$ar = array_replace($ar,
    array_fill_keys(
        array_keys($ar, $value),
        $replacement
    )
);

Instead of a function that only replaces occurrences of one value in an array, there's the more general array_map:

array_map(function ($v) use ($value, $replacement) {
    return $v == $value ? $replacement : $v;
}, $arr);

To replace multiple occurrences of multiple values using array of value => replacement:

array_map(function ($v) use ($replacement) {
    return isset($replacement[$v]) ? $replacement[$v] : $v;
}, $arr);

To replace a single occurrence of one value, you'd use array_search as you do. Because the implementation is so short, there isn't much reason for the PHP developers to create a standard function to perform the task. Not to say that it doesn't make sense for you to create such a function, if you find yourself needing it often.