PHP array_merge() function
In this chapter you will learn:
- Definition for PHP array_merge() function
- Syntax for PHP array_merge() function
- Parameter for PHP array_merge() function
- Note for PHP array_merge() function
- Example - Update associate arrays
- Example - Indexed key got reindexed
- Example - Use array_merge() to reindex an indexed array
- Example - merge associate array
- Example - + vs array_merge()
Definition
The array_merge() function combines two or more arrays.
array_merge() renumbers numerical indexes and merges string indexes.
Syntax
PHP array_merge() function has the following syntax.
array array_merge ( array arr1 [, array arr2 [, array ...]] )Parameter
| Parameter | Is Required | Description |
|---|---|---|
| array1 | Required. | Array to merge |
| array2 | Optional. | Array to merge |
| array3,... | Optional. | Array to merge |
Note
If you want to join two or more arrays together to produce one big array, you need the array_merge() function.
array_merge() joins the array elements of the arrays together to produce the final array. array_push(), array_unshift(), and the square bracket syntax all insert array arguments to produce multidimensional arrays:
<?PHP/* j av a 2 s.co m*/
$authors = array( "Java", "PHP" );
$moreAuthors = array( "CSS", "MySQL" );
array_push( $authors, $moreAuthors );
print_r( $authors );
?>
The code above generates the following result.
array_merge() preserves the keys of associative arrays, so we can use it to add new key/value pairs to an associative array:
<?PHP//from j a v a 2 s . c o m
$myBook = array( "title" => "Learn PHP from java2s.com",
"author" => "java2s.com",
"pubYear" => 2000 );
$myBook = array_merge( $myBook, array( "numPages" => 464 ) );
print_r ( $myBook );
?>
The code above generates the following result.
Example 1
If you add a key/value pair using a string key existing in the array, the original element gets overwritten. This makes array_merge() useful for updating associative arrays:
<?PHP/*from j a va 2s. c o m*/
$myBook = array( "title" => "Learn PHP from java2s.com",
"author" => "java2s.com",
"pubYear" => 2000 );
$myBook = array_merge( $myBook, array( "title" => "java from java2s.com", "pubYear" => 1952 ) );
print_r ( $myBook );
?>
The code above generates the following result.
Example 2
An element with the same numeric key doesn't get overwritten; instead the new element is added to the end of the array and given a new index:
<?PHP/*j a v a 2 s. co m*/
$authors = array( "Java", "PHP", "CSS", "HTML" );
$authors = array_merge( $authors, array( 0 => "MySQL" ) );
print_r ( $authors );
?>
The code above generates the following result.
Example 3
Use array_merge() to reindex an indexed array by passing the array as the parameter. This ensures that all the elements of an indexed array are consecutively indexed:
<?PHP
$authors = array( 4 => "Java", 2 => "PHP", 5 => "CSS", 7 => "HTML" );
print_r( array_merge( $authors ) );
?>
The code above generates the following result.
Example 4
Merge associate array
<?php/* ja v a2 s. c om*/
$toppings1 = array("A", "B", "C", "D");
$toppings2 = array("D", "java2s.com", "PHP");
$both_toppings = array_merge($toppings1, $toppings2);
var_dump($both_toppings);
?>
The code above generates the following result.
Example 5
The + operator in PHP is overloaded so that you can use it to merge
arrays, e.g., $array3 = $array1 + $array2.
If PHP finds any keys in
the second array that clash with the keys in the first array, they will
be skipped.
<?PHP//from j a v a 2 s.com
$arr1 = array("A"=>1, "B"=>2, "C"=>3);
$arr2 = array("B"=>3, "C"=>8);
$arr3 = $arr1 + $arr2;
var_dump(array_merge($arr1, $arr2));
?>
The code above generates the following result.
Next chapter...
What you will learn in the next chapter:
- Definition for PHP array_merge_recursive() Function
- Syntax for PHP array_merge_recursive() Function
- Parameter for PHP array_merge_recursive() Function
- Example - Merge two array recursively