Remove all elements in array matching a specific string using PHP

Question

I'm hoping this is really simple, and I'm missing something obvious!

I'm trying to remove all elements in an array that match a certain string. It's a basic 1D array.

array("Value1", "Value2", "Value3", "Remove", "Remove");

I want to end up with

array("Value1", "Value2", "Value3");

Why does array_filter($array, "Remove"); not work?

Thanks.

Because you're using it incorrectly. php.net/manual/en/function.array-filter.php see examples. — sachleen
– sachleen, Commented Dec 29, 2012 at 2:31
It accepts a callback. array_filter($array, function($a) {return $a !== "Remove";}); — Michael Berkowski
– Michael Berkowski, Commented Dec 29, 2012 at 2:33
I understand the examples use functions, but I don't understand what they are returning? Is there not a simple way to do it without building a handler function? — Craig Wilson
– Craig Wilson, Commented Dec 29, 2012 at 2:33
@CraigWilson The simpler way is with a PHP 5.3+ anonymous function as in my comment above. — Michael Berkowski
– Michael Berkowski, Commented Dec 29, 2012 at 2:34

mario · Accepted Answer · 2012-12-29 02:36:00Z

25

You can just use array_diff here, if it's one fixed string:

$array = array_diff($array, array("Remove"));

For more complex matching, I'd use preg_grep obviously:

$array = preg_grep("/^Remove$/i", $array, PREG_GREP_INVERT);
// matches upper and lowercase for example

answered Dec 29, 2012 at 2:36

mario

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4 Comments

Shiplu Mokaddim Over a year ago

Regular expressions are usually slower for large data-set.

mario Over a year ago

@shiplu For small data sets moreso. The regex compilation is done just once. Which is where the overhead is. PCRE is oftentimes faster for string processing, in this case possibly also the array processing, as most of it operates in C, not as PHP bytecode in the Zend VM.

Avatar Over a year ago

Tip: You probably want to use $array = array_values($array); for reindexing, right after array_diff to not run into PHP error warnings of undefined array indices.

Jack G Nov 24, 2024 at 18:02

Warning/notice: if "Remove" was not found in $array, then it will be added to it. array_diff is orderless and creates an array consisting of entries found in none. Thus, the first line of code acts as a toggle that removes "Removes" if its there or adds it in if it wasnt found.

Shiplu Mokaddim · Accepted Answer · 2012-12-29 02:41:48Z

7

You need to use a callback.

array_filter($array, function($e){
   return stripos("Remove", $e)===false
});

To understand above code properly see this commented code.

array_filter($array, function($e){
    if(stripos("Remove", $e)===false) // "Remove" is not found
        return true; // true to keep it.
    else
        return false; // false to filter it. 
});

edited Dec 29, 2012 at 2:41

answered Dec 29, 2012 at 2:34

Shiplu Mokaddim

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1 Comment

Genki Over a year ago

The tutorial is appreciated! My IDE complained, so I added a semi-colon: return stripos("Remove", $e)===false;

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