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.