PHP foreach pass value or pass reference

The use of foreach () in PHP

foreach () has two uses:

1:

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foreach (Array_Name as $value) { Statement }

The array_name here is the array name you want to traverse, each time the value of the current element of the Array_Name array is assigned to the $value, and the subscript inside the array is moved down one step, which is the next loop to get the next element.

2:

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foreach (Array_Name as $key => $value) { Statement }

The difference between this and the first method is the addition of a $key, in which the key value of the current element is assigned to the variable $key in every loop, except for assigning the value of the current element to $value. The key value can be either a subscript value or a string. For example, "0" in Book[0]=1, "id" in book[id]= "001".

Look at the following example:

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$arr = Array ( Array (' ID ' => 1, ' name ' => ' name1 '), Array (' ID ' => 2, ' name ' => ' name2 '), ); foreach ($arr as $obj) { $obj [' id '] = $obj [' id ']; $obj [' name '] = $obj [' name ']. '-modify '; } Print_r ($arr); Results of output Array ( [0] => Array ( [ID] => 1 [Name] => name1 ) [1] => Array ( [ID] => 2 [Name] => name2 ) )

Observations can be found that the $arr operation does not affect the $arr element in the Foreach loop, so the assignment here is to pass a value instead of a reference. What if you need to modify the value of the elements in the $arr? You can add a "&" symbol in front of the variable, for example:

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foreach ($arr as & $obj) { $obj [' id '] = $obj [' id ']; $obj [' name '] = $obj [' name ']. '-modify '; }

To see another example, the array contains object,

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$arr = Array ( (object) (Array (' ID ' => 1, ' name ' => ' name1 ')), (object) (Array (' ID ' => 2, ' name ' => ' name2 ')), ); foreach ($arr as $obj) { $obj->name = $obj->name. '-modify '; } Print_r ($arr); Results of output Array ( [0] => StdClass Object ( [ID] => 1 [Name] => name1-modify ) [1] => StdClass Object ( [ID] => 2 [Name] => name2-modify ) )

At this point you can see that the object objects in the original array have been modified, so the assignment here is a reference rather than a pass value

To synthesize the above, the conclusion: If the array contains a common type of elements is to use the value of the way, the object type element is used to address the way.