Значение выбранного элемента php
// Before php 5.4
$array = array(1,2,3);
// since php 5.4 , short syntax
$array = [1,2,3];
// I recommend using the short syntax if you have php version >= 5.4
Used to creating arrays like this in Perl?
Looks like we need the range() function in PHP:
$array = array_merge (array( ‘All’ ), range ( ‘A’ , ‘Z’ ));
?>
You don’t need to array_merge if it’s just one range:
There is another kind of array (php>= 5.3.0) produced by
$array = new SplFixedArray(5);
Standard arrays, as documented here, are marvellously flexible and, due to the underlying hashtable, extremely fast for certain kinds of lookup operation.
Supposing a large string-keyed array
$arr=[‘string1’=>$data1, ‘string2’=>$data2 etc. ]
when getting the keyed data with
php does *not* have to search through the array comparing each key string to the given key (‘string1’) one by one, which could take a long time with a large array. Instead the hashtable means that php takes the given key string and computes from it the memory location of the keyed data, and then instantly retrieves the data. Marvellous! And so quick. And no need to know anything about hashtables as it’s all hidden away.
However, there is a lot of overhead in that. It uses lots of memory, as hashtables tend to (also nearly doubling on a 64bit server), and should be significantly slower for integer keyed arrays than old-fashioned (non-hashtable) integer-keyed arrays. For that see more on SplFixedArray :
Unlike a standard php (hashtabled) array, if you lookup by integer then the integer itself denotes the memory location of the data, no hashtable computation on the integer key needed. This is much quicker. It’s also quicker to build the array compared to the complex operations needed for hashtables. And it uses a lot less memory as there is no hashtable data structure. This is really an optimisation decision, but in some cases of large integer keyed arrays it may significantly reduce server memory and increase performance (including the avoiding of expensive memory deallocation of hashtable arrays at the exiting of the script).
When creating arrays , if we have an element with the same value as another element from the same array, we would expect PHP instead of creating new zval container to increase the refcount and point the duplicate symbol to the same zval. This is true except for value type integer.
Example:
$arr = [‘bebe’ => ‘Bob’, ‘age’ => 23, ‘too’ => 23 ];
xdebug_debug_zval( ‘arr’ );
(refcount=2, is_ref=0)
array (size=3)
‘bebe’ => (refcount=1, is_ref=0)string ‘Bob’ (length=3)
‘age’ => (refcount=0, is_ref=0)int 23
‘too’ => (refcount=0, is_ref=0)int 23
but :
$arr = [‘bebe’ => ‘Bob’, ‘age’ => 23, ‘too’ => ’23’ ];
xdebug_debug_zval( ‘arr’ );
(refcount=2, is_ref=0)
array (size=3)
‘bebe’ => (refcount=1, is_ref=0)string ‘Bob’ (length=3)
‘age’ => (refcount=0, is_ref=0)int 23
‘too’ => (refcount=1, is_ref=0)string ’23’ (length=2)
or :
$arr = [‘bebe’ => ‘Bob’, ‘age’ => [1,2], ‘too’ => [1,2] ];
xdebug_debug_zval( ‘arr’ );
(refcount=2, is_ref=0)
array (size=3)
‘bebe’ => (refcount=1, is_ref=0)string ‘Bob’ (length=3)
‘age’ => (refcount=2, is_ref=0)
array (size=2)
0 => (refcount=0, is_ref=0)int 1
1 => (refcount=0, is_ref=0)int 2
‘too’ => (refcount=2, is_ref=0)
array (size=2)
0 => (refcount=0, is_ref=0)int 1
1 => (refcount=0, is_ref=0)int 2
This function makes (assoc.) array creation much easier:
function arr (. $array )< return $array ; >
?>
It allows for short syntax like:
$arr = arr ( x : 1 , y : 2 , z : 3 );
?>
Instead of:
$arr = [ «x» => 1 , «y» => 2 , «z» => 3 ];
// or
$arr2 = array( «x» => 1 , «y» => 2 , «z» => 3 );
?>
Sadly PHP 8.2 doesn’t support this named arguments in the «array» function/language construct.
array_search
Note:
If needle is a string, the comparison is done in a case-sensitive manner.
If the third parameter strict is set to true then the array_search() function will search for identical elements in the haystack . This means it will also perform a strict type comparison of the needle in the haystack , and objects must be the same instance.
Return Values
Returns the key for needle if it is found in the array, false otherwise.
If needle is found in haystack more than once, the first matching key is returned. To return the keys for all matching values, use array_keys() with the optional search_value parameter instead.
This function may return Boolean false , but may also return a non-Boolean value which evaluates to false . Please read the section on Booleans for more information. Use the === operator for testing the return value of this function.
Examples
Example #1 array_search() example
$array = array( 0 => ‘blue’ , 1 => ‘red’ , 2 => ‘green’ , 3 => ‘red’ );
$key = array_search ( ‘green’ , $array ); // $key = 2;
$key = array_search ( ‘red’ , $array ); // $key = 1;
?>
See Also
- array_keys() — Return all the keys or a subset of the keys of an array
- array_values() — Return all the values of an array
- array_key_exists() — Checks if the given key or index exists in the array
- in_array() — Checks if a value exists in an array
User Contributed Notes 16 notes
About searcing in multi-dimentional arrays; two notes on «xfoxawy at gmail dot com»;
It perfectly searches through multi-dimentional arrays combined with array_column() (min php 5.5.0) but it may not return the values you’d expect.
Since array_column() will produce a resulting array; it won’t preserve your multi-dimentional array’s keys. So if you check against your keys, it will fail.
$people = array(
2 => array(
‘name’ => ‘John’ ,
‘fav_color’ => ‘green’
),
5 => array(
‘name’ => ‘Samuel’ ,
‘fav_color’ => ‘blue’
)
);
$found_key = array_search ( ‘blue’ , array_column ( $people , ‘fav_color’ ));
?>
Here, you could expect that the $found_key would be «5» but it’s NOT. It will be 1. Since it’s the second element of the produced array by the array_column() function.
Secondly, if your array is big, I would recommend you to first assign a new variable so that it wouldn’t call array_column() for each element it searches. For a better performance, you could do;
$colors = array_column ( $people , ‘fav_color’ );
$found_key = array_search ( ‘blue’ , $colors );
?>
If you are using the result of array_search in a condition statement, make sure you use the === operator instead of == to test whether or not it found a match. Otherwise, searching through an array with numeric indicies will result in index 0 always getting evaluated as false/null. This nuance cost me a lot of time and sanity, so I hope this helps someone. In case you don’t know what I’m talking about, here’s an example:
$code = array( «a» , «b» , «a» , «c» , «a» , «b» , «b» ); // infamous abacabb mortal kombat code 😛
// this is WRONG
while (( $key = array_search ( «a» , $code )) != NULL )
<
// infinite loop, regardless of the unset
unset( $code [ $key ]);
>
// this is _RIGHT_
while (( $key = array_search ( «a» , $code )) !== NULL )
<
// loop will terminate
unset( $code [ $key ]);
>
?>
for searching case insensitive better this:
array_search ( strtolower ( $element ), array_map ( ‘strtolower’ , $array ));
?>
var_dump ( array_search ( ‘needle’ , [ 0 => 0 ])); // int(0) (!)
var_dump ( array_search ( ‘needle’ , [ 0 => 0 ], true )); // bool(false)
var_dump ( array_search ( ‘needle’ , [ 0 => 0 ])); // bool(false)
To expand on previous comments, here are some examples of
where using array_search within an IF statement can go
wrong when you want to use the array key thats returned.
Take the following two arrays you wish to search:
$fruit_array = array( «apple» , «pear» , «orange» );
$fruit_array = array( «a» => «apple» , «b» => «pear» , «c» => «orange» );
if ( $i = array_search ( «apple» , $fruit_array ))
//PROBLEM: the first array returns a key of 0 and IF treats it as FALSE
if ( is_numeric ( $i = array_search ( «apple» , $fruit_array )))
//PROBLEM: works on numeric keys of the first array but fails on the second
if ( $i = is_numeric ( array_search ( «apple» , $fruit_array )))
//PROBLEM: using the above in the wrong order causes $i to always equal 1
if ( $i = array_search ( «apple» , $fruit_array ) !== FALSE )
//PROBLEM: explicit with no extra brackets causes $i to always equal 1
if (( $i = array_search ( «apple» , $fruit_array )) !== FALSE )
//YES: works on both arrays returning their keys
?>
Despite PHP’s amazing assortment of array functions and juggling maneuvers, I found myself needing a way to get the FULL array key mapping to a specific value. This function does that, and returns an array of the appropriate keys to get to said (first) value occurrence.
function array_recursive_search_key_map($needle, $haystack) foreach($haystack as $first_level_key=>$value) if ($needle === $value) return array($first_level_key);
> elseif (is_array($value)) $callback = array_recursive_search_key_map($needle, $value);
if ($callback) return array_merge(array($first_level_key), $callback);
>
>
>
return false;
>
$nested_array = $sample_array = array(
‘a’ => array(
‘one’ => array (‘aaa’ => ‘apple’, ‘bbb’ => ‘berry’, ‘ccc’ => ‘cantalope’),
‘two’ => array (‘ddd’ => ‘dog’, ‘eee’ => ‘elephant’, ‘fff’ => ‘fox’)
),
‘b’ => array(
‘three’ => array (‘ggg’ => ‘glad’, ‘hhh’ => ‘happy’, ‘iii’ => ‘insane’),
‘four’ => array (‘jjj’ => ‘jim’, ‘kkk’ => ‘kim’, ‘lll’ => ‘liam’)
),
‘c’ => array(
‘five’ => array (‘mmm’ => ‘mow’, ‘nnn’ => ‘no’, ‘ooo’ => ‘ohh’),
‘six’ => array (‘ppp’ => ‘pidgeon’, ‘qqq’ => ‘quail’, ‘rrr’ => ‘rooster’)
)
);
$array_keymap = array_recursive_search_key_map($search_value, $nested_array);
But again, with the above solution, PHP again falls short on how to dynamically access a specific element’s value within the nested array. For that, I wrote a 2nd function to pull the value that was mapped above.
function array_get_nested_value($keymap, $array)
$nest_depth = sizeof($keymap);
$value = $array;
for ($i = 0; $i < $nest_depth; $i++) $value = $value[$keymap[$i]];
>
usage example:
——————-
echo array_get_nested_value($array_keymap, $nested_array); // insane