Unix and Linux Discussions Tagged with empty |
|
Thread / Thread Starter |
Last Post |
Replies |
Views |
Forum |
|
|
|
2 |
39,058 |
Shell Programming and Scripting |
|
|
|
2 |
16,443 |
UNIX for Beginners Questions & Answers |
|
|
|
7 |
11,716 |
UNIX for Beginners Questions & Answers |
|
|
|
7 |
4,257 |
Programming |
|
|
|
0 |
13,564 |
Shell Programming and Scripting |
|
|
|
4 |
3,564 |
UNIX for Dummies Questions & Answers |
|
|
|
2 |
5,638 |
UNIX for Dummies Questions & Answers |
|
|
|
5 |
15,247 |
Shell Programming and Scripting |
|
|
|
7 |
17,160 |
Shell Programming and Scripting |
|
|
|
6 |
5,345 |
Shell Programming and Scripting |
|
|
|
12 |
5,716 |
Shell Programming and Scripting |
|
|
|
2 |
15,825 |
UNIX for Dummies Questions & Answers |
|
|
|
9 |
6,015 |
HP-UX |
|
|
|
1 |
22,667 |
UNIX for Dummies Questions & Answers |
|
|
|
4 |
2,009 |
Shell Programming and Scripting |
|
|
|
2 |
4,450 |
Programming |
|
|
|
1 |
4,014 |
Shell Programming and Scripting |
|
|
|
2 |
10,617 |
UNIX for Dummies Questions & Answers |
|
|
|
4 |
19,599 |
Shell Programming and Scripting |
|
|
|
5 |
8,288 |
UNIX for Dummies Questions & Answers |
|
|
|
3 |
3,496 |
Shell Programming and Scripting |
|
|
|
0 |
1,010 |
Software Releases - RSS News |
|
|
|
1 |
26,692 |
UNIX for Dummies Questions & Answers |
|
|
|
4 |
4,277 |
UNIX for Dummies Questions & Answers |
|
|
|
12 |
114,275 |
Shell Programming and Scripting |
|
|
|
7 |
25,698 |
UNIX for Dummies Questions & Answers |
|
|
|
2 |
235,181 |
UNIX for Dummies Questions & Answers |
|
|
|
2 |
66,008 |
UNIX for Dummies Questions & Answers |
|
|
|
4 |
3,111 |
Shell Programming and Scripting |
|
|
|
8 |
44,904 |
UNIX for Dummies Questions & Answers |
|
|
|
2 |
7,458 |
Shell Programming and Scripting |
|
|
|
2 |
4,592 |
UNIX for Dummies Questions & Answers |
|
|
|
1 |
3,359 |
UNIX for Dummies Questions & Answers |
|
|
|
13 |
10,882 |
UNIX for Dummies Questions & Answers |
|
|
|
3 |
3,967 |
Programming |
|
|
|
2 |
3,220 |
UNIX for Dummies Questions & Answers |
|
|
|
5 |
3,770 |
UNIX for Dummies Questions & Answers |
|
|
|
2 |
8,897 |
UNIX for Dummies Questions & Answers |
|
|
|
6 |
4,294 |
UNIX for Dummies Questions & Answers |
|
|
|
2 |
2,755 |
UNIX for Dummies Questions & Answers |
EMPTY(3) 1 EMPTY(3)
empty - Determine whether a variable is empty
SYNOPSIS
bool empty (mixed $var)
DESCRIPTION
Determine whether a variable is considered to be empty. A variable is considered empty if it does not exist or if its value equals FALSE.
empty(3) does not generate a warning if the variable does not exist.
PARAMETERS
o $var
- Variable to be checked
Note
Prior to PHP 5.5, empty(3) only supports variables; anything else will result in a parse error. In other words, the follow-
ing will not work: empty(trim($name)). Instead, use trim($name) == false.
No warning is generated if the variable does not exist. That means empty(3) is essentially the concise equivalent to !isset($var)
|| $var == false.
RETURN VALUES
Returns FALSE if $var exists and has a non-empty, non-zero value. Otherwise returns TRUE.
The following things are considered to be empty:
o "" (an empty string)
o 0 (0 as an integer)
o 0.0 (0 as a float)
o "0" (0 as a string)
o NULL
o FALSE
o array() (an empty array)
o $var; (a variable declared, but without a value)
CHANGELOG
+--------+---------------------------------------------------+
|Version | |
| | |
| | Description |
| | |
+--------+---------------------------------------------------+
| 5.5.0 | |
| | |
| | empty(3) now supports expressions, rather than |
| | only variables. |
| | |
| 5.4.0 | |
| | |
| | Checking non-numeric offsets of strings returns |
| | TRUE. |
| | |
+--------+---------------------------------------------------+
EXAMPLES
Example #1
A simple empty(3) / isset(3) comparison.
<?php
$var = 0;
// Evaluates to true because $var is empty
if (empty($var)) {
echo '$var is either 0, empty, or not set at all';
}
// Evaluates as true because $var is set
if (isset($var)) {
echo '$var is set even though it is empty';
}
?>
Example #2
empty(3) on String Offsets
PHP 5.4 changes how empty(3) behaves when passed string offsets.
<?php
$expected_array_got_string = 'somestring';
var_dump(empty($expected_array_got_string['some_key']));
var_dump(empty($expected_array_got_string[0]));
var_dump(empty($expected_array_got_string['0']));
var_dump(empty($expected_array_got_string[0.5]));
var_dump(empty($expected_array_got_string['0.5']));
var_dump(empty($expected_array_got_string['0 Mostel']));
?>
Output of the above example in PHP 5.3:
bool(false)
bool(false)
bool(false)
bool(false)
bool(false)
bool(false)
Output of the above example in PHP 5.4:
bool(true)
bool(false)
bool(false)
bool(false)
bool(true)
bool(true)
NOTES
Note
Because this is a language construct and not a function, it cannot be called using variable functions.
Note
When using empty(3) on inaccessible object properties, the __isset() overloading method will be called, if declared.
SEE ALSO
isset(3), __isset(), unset(3), array_key_exists(3), count(3), strlen(3), The type comparison tables.
PHP Documentation Group EMPTY(3)