Arrays: array_shift($arr) or $arr[0]?

Which one would you use?

Basically I 开发者_如何学编程only want to get the 1st element from a array, that's it.

Well, they do different things.

• array_shift($arr) takes the first element out of the array, and gives it to you.

• $arr[0] just gives it to you... if the array has numeric keys.

An alternative that works for associative arrays too is reset($arr). This does move the array's internal pointer, but unless you're using those functions this is unlikely to affect you.

array_shift will actually remove the specified value from the array. Do not use it unless you really want to reduce the array!

See here: http://php.net/manual/en/function.array-shift.php

You would use $arr[ 0 ]; array_shift removes the first element from the array.

EDIT

This answer is actually somewhere between incomplete and plain out wrong but, because the comments of the two jon's I think that it should actually stay up so that others can see that discourse.

The right answer:

• reset is the method to return the first defined index of the array. Even in non-associative arrays, this may not be the 0 index.
• array_shift will remove and return the value which is found at reset

The OP made the assumption that $arr[0] is the first index is not accurate in that particular context.

$arr[0] only works if the array as numerical keys.

array_shift removes the element from the array and it modifies the array itself.

If you are not sure what the first key is , and you do not want to remove it from the array, you could use:

<?php
foreach($arr $k=>$v){
   $value = $v;
   break;
}

or even better:

<?php
reset($arr);
$value = current($arr);

If you have an associative Array you can also use reset($arr): It returns the first Element (doesn't remove), and sets the array pointer to this element.

But the fastest way is $arr[0].

Do you want to modify the arr array also? array_shift removes the first element of the array and returns it, thus the array has changed. $arr[0] merely gives you the first element.

I would use $arr[0] unless I explicitly wanted to modify the array. You may add code later to use the arr array and forget that it was modified.

given what you need, $arr[0] is preferrable, because it's faster. array_shift is used in other situations.

arrshift is more reliable and will always return the first element in the array, but this also modifies the array by removing that element.

arr[0] will fail if your array doesn't start at the 0 index, but leaves the array itself alone.

A more convoluted but reliable method is:

$keys = array_keys($arr);
$first = $arr[$keys[0]];

with array_shif you have two operations:

1. retrive the firs element
2. shift the array

if you access by index, actually you have only one operation.

If you want the first element of an array, use $arr[0] form. Advantages - Simplicity, Readability and Maintainability. Keep things straight forward.

Edit: Use index 0 only if you know that the array has default keys starting from 0.

If you don't want to change the array in question, use $arr[0] (which merely gets the first element), otherwise if you want to remove the first element of $arr from $arr, use array_shift($arr).

For example:

$arr=array(3,-6,2);
$foo=$arr[0]; //$foo==3 and $arr==array(3,-6,2).
$bar=array_shift($arr); //$bar==3 and $arr==array(-6,2).

ETA: As others have pointed out, be sure that your array isn't an associative array (ie the keys are 0,1,...,(sizeof($arr)-1)), otherwise this probably won't work.