Get the first element of an array

$arr = $array = array( 9 => 'apple', 7 => 'orange', 13 => 'plum' );
echo reset($arr); // echoes 'apple'

If you don't want to lose the current pointer position, just create an alias for the array.

PHP 7.3 added two functions for getting the first and the last key of an array directly without modification of the original array and without creating any temporary objects:

• array_key_first
• array_key_last

Apart from being semantically meaningful, these functions don't even move the array pointer (as foreach would do).

Having the keys, one can get the values by the keys directly.

Examples (all of them require PHP 7.3+)

Getting the first/last key and value:

$my_array = ['IT', 'rules', 'the', 'world'];

$first_key = array_key_first($my_array);
$first_value = $my_array[$first_key];

$last_key = array_key_last($my_array);
$last_value = $my_array[$last_key];

Getting the first/last value as one-liners, assuming the array cannot be empty:

$first_value = $my_array[ array_key_first($my_array) ];

$last_value = $my_array[ array_key_last($my_array) ];

Getting the first/last value as one-liners, with defaults for empty arrays:

$first_value = empty($my_array) ? 'default' : $my_array[ array_key_first($my_array) ];

$last_value = empty($my_array) ? 'default' : $my_array[ array_key_last($my_array) ];

You can get the Nth element with a language construct, "list":

// First item
list($firstItem) = $yourArray;

// First item from an array that is returned from a function
list($firstItem) = functionThatReturnsArray();

// Second item
list( , $secondItem) = $yourArray;

With the array_keys function you can do the same for keys:

list($firstKey) = array_keys($yourArray);
list(, $secondKey) = array_keys($yourArray);

Keep this simple! There are lots of correct answers here, but to minimize all the confusion, these two work and reduce a lot of overhead:

key($array) gets the first key of an array
current($array) gets the first value of an array

EDIT:
Regarding the comments below. The following example will output: string(13) "PHP code test"

$array = array
(
   '1'           => 'PHP code test',  
   'foo'         => 'bar', 5 , 5 => 89009, 
   'case'        => 'Random Stuff: '.rand(100,999),
   'PHP Version' => phpversion(),
   0             => 'ending text here'
);

var_dump(current($array));

PHP 7.3 added two functions for getting the first and the last key of an array directly without modification of the original array and without creating any temporary objects:

• array_key_first
• array_key_last

"There are several ways to provide this functionality for versions prior to PHP 7.3.0. It is possible to use array_keys(), but that may be rather inefficient. It is also possible to use reset() and key(), but that may change the internal array pointer. An efficient solution, which does not change the internal array pointer, written as polyfill:"

<?php
if (!function_exists('array_key_first')) {
    function array_key_first($arr) {
        foreach($arr as $key => $unused) {
            return $key;
        }
        return NULL;
    }
}

if (!function_exists('array_key_last')) {
    function array_key_last($arr) {
        return array_key_first(array_reverse($arr, true));
    }
}
?>

A kludgy way is:

$foo = array( 4 => 'apple', 7 => 'orange', 13 => 'plum' );

function get_first ($foo) {
    foreach ($foo as $k=>$v){
        return $v;
    }
}

print get_first($foo);

Most of these work! BUT for a quick single line (low resource) call:

$array = array( 4 => 'apple', 7 => 'orange', 13 => 'plum' );
echo $array[key($array)];

// key($array) -> will return the first key (which is 4 in this example)

Although this works, and decently well, please also see my additional answer: https://stackoverflow.com/a/48410351/1804013

Use:

$first = array_slice($array, 0, 1);  
$val= $first[0];

By default, array_slice does not preserve keys, so we can safely use zero as the index.

<?php
    $arr = array(3 => "Apple", 5 => "Ball", 11 => "Cat");
    echo array_values($arr)[0]; // Outputs: Apple
?>

Other Example:

<?php
    $arr = array(3 => "Apple", 5 => "Ball", 11 => "Cat");
    echo current($arr); // Outputs: Apple
    echo reset($arr); // Outputs: Apple
    echo next($arr); // Outputs: Ball
    echo current($arr); // Outputs: Ball
    echo reset($arr); // Outputs: Apple
?>

I think using array_values would be your best bet here. You could return the value at index zero from the result of that function to get 'apple'.

No one has suggested using the ArrayIterator class:

$array = array( 4 => 'apple', 7 => 'orange', 13 => 'plum' );
$first_element = (new ArrayIterator($array))->current();
echo $first_element; //'apple'

gets around the by reference stipulation of the OP.

One line closure, copy, reset:

<?php

$fruits = array(4 => 'apple', 7 => 'orange', 13 => 'plum');

echo (function() use ($fruits) { return reset($fruits); })();

Output:

apple

Alternatively the shorter short arrow function:

echo (fn() => reset($fruits))();

This uses by-value variable binding as above. Both will not mutate the original pointer.