Verifying If a Key Exists in an Array in PHP

Home > PHP

Q

How Do You Know If a Key Is Defined in an Array in PHP?

✍: FYIcenter.com

A

There are two functions can be used to test if a key is defined in an array or not:

array_key_exists($key, $array) - Returns true if the $key is defined in $array.
isset($array[$key]) - Returns true if the $key is defined in $array.

Here is a PHP example script:

<?php 
$array = array("Zero"=>"PHP", "One"=>"Perl", "Two"=>"Java");
print("Is 'One' defined? ".array_key_exists("One", $array)."\n");
print("Is '1' defined? ".array_key_exists("1", $array)."\n");
print("Is 'Two' defined? ".isset($array["Two"])."\n");
print("Is '2' defined? ".isset($array[2])."\n");
?>

This script will print:

Is 'One' defined? 1
Is '1' defined?
Is 'Two' defined? 1
Is '2' defined?

⇒ Finding a Given Value in an Array in PHP

⇐ Counting the Number of Values in an Array in PHP

⇑ PHP Built-in Functions for Arrays

⇑⇑ PHP Tutorials

2017-01-29, ∼1934🔥, 0💬

PHP Built-in Functions for Arrays
Where to find tutorials on how to use PHP built-in functions to manage arrays? A collection of tutorials to answer many frequently asked questions on how to PHP functions to manage arrays. Clear answers are provided with tutorial exercises on searching keys and values, sorting arrays, merging two ar... 2017-01-29, ∼2852🔥, 0💬

Retrieving All Values from an Array in PHP
How To Get All the Values Out of an Array in PHP? Function array_values() returns a new array that contains all the values of a given array. Here is a PHP script on how to use array_values(): <?php $mixed = array(); $mixed["Zero"] = "PHP"; $mixed[1] = "Perl"; $mixed["Two"] = "Java"; $mixed["3... 2017-01-21, ∼2506🔥, 0💬

Counting the Number of Values in an Array in PHP
How To Get the Total Number of Values in an Array in PHP? You can get the total number of values in an array by using the count() function. Here is a PHP example script: <?php $array = array("PHP", "Perl", "Java"); print_r("Size 1: ".count($array)."\n"); $array = array(); print_r("Size 2: ".c... 2017-01-29, ∼2445🔥, 0💬

Sorting an Array by Values in PHP
How To Sort an Array by Values in PHP? Sorting an array by values is doable by using the sort() function. It will re-order all pairs of keys and values based on the alphanumeric order of the values. Then it will replace all keys with integer keys sequentially starting with 0. So using sort() on arra... 2017-01-21, ∼2432🔥, 0💬

Sorting an Array by Keys in PHP
How To Sort an Array by Keys in PHP? Sorting an array by keys can be done by using the ksort() function. It will re-order all pairs of keys and values based on the alphanumeric order of the keys. Here is a PHP script on how to use ksort(): <?php $mixed = array(); $mixed["Zero"] = "PHP"; $mixe... 2017-01-21, ∼2355🔥, 0💬

Finding a Given Value in an Array in PHP
How To Find a Specific Value in an Array in PHP? There are two functions can be used to test if a value is defined in an array or not: array_search($value, $array) - Returns the first key of the matching value in the array, if found. Otherwise, it returns false. in_array($value, $array) - Returns tr... 2017-01-21, ∼2314🔥, 0💬

Order of Array Values in PHP
How the Values Are Ordered in an Array in PHP? PHP says that an array is an ordered map. But how the values are ordered in an array? The answer is simple. Values are stored in the same order as they are inserted like a queue. If you want to reorder them differently, you need to use a sort function. ... 2017-01-29, ∼2278🔥, 0💬

Looping through an Array in PHP
How to Loop through an Array in PHP? The best way to loop through an array is to use the "foreach" statement. There are two forms of "foreach" statements: foreach ($array as $value) {} - This gives you only one temporary variable to hold the current value in the array. foreach ($array as $key=&g... 2017-02-03, ∼2187🔥, 0💬

Retrieving All Keys from an Array in PHP
How To Get All the Keys Out of an Array in PHP? Function array_keys() returns a new array that contains all the keys of a given array. Here is a PHP script on how to use array_keys(): <?php $mixed = array(); $mixed["Zero"] = "PHP"; $mixed[1] = "Perl"; $mixed["Two"] = "Java"; $mixed["3"] = "C+... 2017-01-21, ∼2111🔥, 0💬

All rights in the contents of this web site are reserved by the individual author. fyicenter.com does not guarantee the truthfulness, accuracy, or reliability of any contents.