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How do I find out if a value is already in an array?


If you don't have a particular requirement for this at the moment, then almost certainly at some time in your PHP programming career you will need to know whether an element is already in an array or not. If it is, you will usually want to take one course of action, and if it isn't, another.

PHP provides a very useful function called in_array that lets you check whether a value is already in the array or not. Here is an example of it in use when we want to check if certain numbers are present in an array or not:

<?php
$numbers 
range(1,10);
$checknumbers = array(1,20,10);
foreach(
$checknumbers as $isitthere) {
if(
in_array($isitthere,$numbers)) { echo "The number $isitthere is in the numbers array\n\n"; }
else { echo 
"The number $isitthere is NOT in the numbers array\n\n"; }
}
?>


This prints:

The number 1 is in the numbers array

The number 20 is NOT in the numbers array

The number 10 is in the numbers array



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How do you remove duplicate values from an array?
I want to invert my array, can I do this?
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How do I add to the end of an array and know how large the array is?