[ACCEPTED]-PHP: Variable empty or not set or what?-conditional

Accepted answer

Score: 23

Check PHP manual out: http://www.php.net/manual/en/types.comparisons.php

Expression  gettype() empty() is_null() isset() if($x)
$x = "";        string  TRUE    FALSE   TRUE    FALSE
$x = null;      NULL    TRUE    TRUE    FALSE   FALSE
var $x;         NULL    TRUE    TRUE    FALSE   FALSE
$x undefined    NULL    TRUE    TRUE    FALSE   FALSE
$x = array();   array   TRUE    FALSE   TRUE    FALSE
$x = false;     boolean TRUE    FALSE   TRUE    FALSE
$x = true;      boolean FALSE   FALSE   TRUE    TRUE
$x = 1;         integer FALSE   FALSE   TRUE    TRUE
$x = 42;        integer FALSE   FALSE   TRUE    TRUE
$x = 0;         integer TRUE    FALSE   TRUE    FALSE
$x = -1;        integer FALSE   FALSE   TRUE    TRUE
$x = "1";       string  FALSE   FALSE   TRUE    TRUE
$x = "0";       string  TRUE    FALSE   TRUE    FALSE
$x = "-1";      string  FALSE   FALSE   TRUE    TRUE
$x = "php";     string  FALSE   FALSE   TRUE    TRUE
$x = "true";    string  FALSE   FALSE   TRUE    TRUE
$x = "false";   string  FALSE   FALSE   TRUE    TRUE

As you can see, if(!empty($x)) is 3 equal to if($x) and if(!is_null($x)) is equal to if(isset($x)). As far as if 2 $data != '' goes, it is TRUE if $data is not NULL, '', FALSE or 0 (loose 1 comparison).

Score: 10

if (isset($data)) {

Variable is just set - before that line 10 we declared new variable with name 'data', i.e. $data 9 = 'abc';

if (!empty($data)) {

Variable is filled with data. It 8 cannot have empty array because then $data has 7 array type but still has no data, i.e. $data 6 = array(1); Cannot be null, empty string, empty 5 array, empty object, 0, etc.

if ($data != '') {

Variable is 4 not an empty string. But also cannot be 3 empty value (examples above).
If we want 2 to compare types, use !== or ===.

if ($data) {

Variable is filled 1 out with any data. Same thing as !empty($data).

Score: 4

They aren't the same.

true if the variable 8 is set. the variable can be set to blank 7 and this would be true.
true if the variable 6 is set and does not equal empty string, 0, '0', NULL, FALSE, blank 5 array. it is clearly not the same as isset.
if 4 the variable does not equal an empty string, if 3 the variable isnt set its an empty string.
if 2 the variable coerces to true, if the variable 1 isnt set it will coerce to false.

Score: 0

if (isset($data)) - Determines if a variable 8 is set (has not bet 'unset()' and is not NULL.

if (!empty($data)) - Is 7 a type agnostic check for empty if $data 6 was '', 0, false, or NULL it would return 5 true.

if ($data != '') { this is a string 4 type safe of checking whether $data is not 3 equal to an empty string

if ($data) { this 2 is a looking for true or false (aka: 0 or 1 1)

Source: stackoverflow.com

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