Easy way to apply a function to an array

alex_31671 0
Viewed 30858

I am aware of array_walk() and array_map(). However when using the former like so (on an old project) it failed

array_walk($_POST, 'mysql_real_escape_string');

Warning: mysql_real_escape_string() expects parameter 2 to be resource, string given.

So I went with this slightly more ugly version

foreach($_POST as $key => $value) {
    $_POST[$key] = mysql_real_escape_string($value);
}

So why didn't the first way work? What is the best way to map values of an array to a function?

arrays php
7 Answers

The callback function passed to array_walk is expected to accept two parameters, one for the value and one for the key:

Typically, funcname takes on two parameters. The array parameter's value being the first, and the key/index second.

But mysql_real_escape_string expects the second parameter to be a resource. That’s why you’re getting that error.

Use array_map instead, it only takes the value of each item and passes it to the given callback function:

array_map('mysql_real_escape_string', $_POST);

The second parameter will be omitted and so the last opened connection is used.

If you need to pass the second parameter, you need to wrap the function call in another function, e.g. an anonymous function:

array_map(function($string) use ($link) { return mysql_real_escape_string($string, $link); }, $_POST);
Gumbo_531140

It's because the mysql_real_escape_string is being given two parameters, both string.

http://php.net/manual/en/function.mysql-real-escape-string.php

http://www.phpbuilder.com/manual/en/function.array-map.php:

array_map() returns an array containing all the elements of arr1 after applying the callback function to each one. The number of parameters that the callback function accepts should match the number of arrays passed to the array_map()

you could do

function myescape($val)
{
    return mysql_real_escape_string($val);
}

... then 

array_walk($_POST, 'myescape');
user_28470

http://php.net/manual/en/function.array-walk.php says that array_walk will call the function with 2 arguments, the value and the key. You should write a new function to wrap mysql_real_escape_string. Something like:

function wrapper($val, $key){
    return mysql_real_escape_string($val);
}

And then:

array_walk($_POST, 'wrapper');

Sorry if my PHP is not correct, but I think you'll catch the general idea.

user_1575190

PHP 7.4 style:

$link = mysqli_connect("localhost", "my_user", "my_password", "world");

array_map(fn($string) => mysqli_real_escape_string($string, $link), $_POST);
user_37237070
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