Merging arrays means combining two or more arrays into a single array. If this is done manually, then the task becomes difficult. Also, the logic of merging two variables as well as coding different memory allocations using other variables takes a lot of time. In this tutorial, you will learn about PHP array_merge() function for merging two or more arrays.
PHP array_merge() Function
array_merge() function is a built-in function of PHP that is used to merge two or more arrays or several elements into a single array. When a given input array matches its string, the subsequent values of the array override its previous counterpart. When your input arrays contain some numeric keys, the latter value will be appended instead of having its original value acquired. If the array_merge () function takes only one array, the array will be indexed numerically, and the keys will be re-indexed in a continuous fashion. This function can be used if you are using PHP version 4.0 or above.
Elements of arrays are merged in a way where the elements of the second array join at the end of the first array. The syntax of using array_merge() function is:
array_merge(array1, array2, array3, ...)
This function will accept a list of arrays that will be separated by a comma as its parameter. These arrays will be joined together using the array_merge() function as shown in the syntax above. You can add N number of arrays (array_merge($arr_1, $arr_2, ……, $arr_n) separated by comma (','). After this function is executed, it will generate a new array in which all the elements of those arrays that are passed as parameters will remain but under one common array-name.
Here is a simple program showing the use of array_merge() to merge two associative arrays into one array.
<?php $arr1=array("g"=>"gold","d"=>"diamond"); $arr2=array("p"=>"platinum","s"=>"silver"); print_r(array_merge($arr1,$arr2)); ?>
Array ( [g] => gold [d] => diamond [p] => platinum [s] => silver )
Another example where only one array will be passed as a parameter in array_merge() but with integer keys.
<?php $arr =array(2 =>"gold", 6 =>"diamond"); print_r(array_merge($arr)); ?>
Array (  => gold  => diamond )