easy way to execute conditional html / javascript / css / other language code with php if else:
<?php if (condition): ?>
html code to run if condition is true
<?php else: ?>
html code to run if condition is false
<?php endif ?>
if
(PHP 4, PHP 5, PHP 7)
Das if-Konstrukt ist eines der wichtigsten Features vieler Programmiersprachen, so auch in PHP, denn es ermöglicht die bedingte Ausführung von Kodefragmenten. PHP bietet eine if-Anweisung die der in C ähnelt:
if (expression) statement
expression wird wie im Abschnitt über Ausdrücke
beschrieben zu einem boolschen Wahrheitswert ausgewertet.
Evaluiert expression zu TRUE so wird
statement von PHP ausgeführt, anderenfalls
wird es ignoriert. Weitere Informationen dazu welche Werte als TRUE
oder FALSE ausgewertet werden können Sie im Abschnitt 'Umwandlung zu
boolean'.
Das folgende Beispiel würde a ist größer als b ausgeben wenn $a größer als $b ist:
<?php
if ($a > $b)
echo "a ist größer als b";
?>
Oft werden Sie mehr als eine Anweisung bedingt ausführen wollen. Dazu ist es natürlich nicht möglich jede Anweisung mit einer eigenen if-Anweisung zu versehen. Sie können statt dessen mehrere Anweisung zu einer Anweisungsgruppe zusammenfassen. So würde z.B. der folgende Programmcode a ist größer als b ausgeben, falls $a größer als $b ist, und den Wert von $a an $b zuweisen:
<?php
if ($a > $b) {
echo "a ist größer als b";
$b = $a;
}
?>
If-Anweisungen können beliebig oft ineinander verschachtelt werden und bieten Ihnen so vollständige Flexibilität für die bedingte Ausführung der verschiedenen Teile Ihres Programs.
add a note
User Contributed Notes 17 notes
robk ¶
4 years ago
Christian L. ¶
7 years ago
An other way for controls is the ternary operator (see Comparison Operators) that can be used as follows:
<?php
$v = 1;
$r = (1 == $v) ? 'Yes' : 'No'; // $r is set to 'Yes'
$r = (3 == $v) ? 'Yes' : 'No'; // $r is set to 'No'
echo (1 == $v) ? 'Yes' : 'No'; // 'Yes' will be printed
// and since PHP 5.3
$v = 'My Value';
$r = ($v) ?: 'No Value'; // $r is set to 'My Value' because $v is evaluated to TRUE
$v = '';
echo ($v) ?: 'No Value'; // 'No Value' will be printed because $v is evaluated to FALSE
?>
Parentheses can be left out in all examples above.
grawity at gmail dot com ¶
10 years ago
re: #80305
Again useful for newbies:
if you need to compare a variable with a value, instead of doing
<?php
if ($foo == 3) bar();
?>
do
<?php
if (3 == $foo) bar();
?>
this way, if you forget a =, it will become
<?php
if (3 = $foo) bar();
?>
and PHP will report an error.
Donny Nyamweya ¶
7 years ago
In addition to the traditional syntax for if (condition) action;
I am fond of the ternary operator that does the same thing, but with fewer words and code to type:
(condition ? action_if_true: action_if_false;)
example
(x > y? 'Passed the test' : 'Failed the test')
cole dot trumbo at nospamthnx dot gmail dot com ¶
10 months ago
Any variables defined inside the if block will be available outside the block. Remember that the if doesn't have its own scope.
<?php
$bool = true;
if ($bool) {
$hi = 'Hello to all people!';
}
echo $hi;
?>
It will print 'Hello to all people!'
On the other hand, this will have no output:
<?php
if (false) {
$hi = 'Hello to all people!';
}
echo $hi;
?>
techguy14 at gmail dot com ¶
7 years ago
You can have 'nested' if statements withing a single if statement, using additional parenthesis.
For example, instead of having:
<?php
if( $a == 1 || $a == 2 ) {
if( $b == 3 || $b == 4 ) {
if( $c == 5 || $ d == 6 ) {
//Do something here.
}
}
}
?>
You could just simply do this:
<?php
if( ($a==1 || $a==2) && ($b==3 || $b==4) && ($c==5 || $c==6) ) {
//do that something here.
}
?>
Hope this helps!
brian at webdesignacademy.co.za ¶
2 years ago
You can also check alphabet characters like this
<?php
// Alphabetical Comparison
$a="brian";
$b="zebra";
if ($a < $b){
echo $a." is before ".$b." in the alphabet";
}
else{
echo $a." is after ".$b." in the alphabet";
}
// Result : brian is before zebra in the alphabet
?>
chrislabricole at yahoo dot fr ¶
9 years ago
You can do IF with this pattern :
<?php
$var = TRUE;
echo $var==TRUE ? 'TRUE' : 'FALSE'; // get TRUE
echo $var==FALSE ? 'TRUE' : 'FALSE'; // get FALSE
?>
admin at leonard !spam challis dot com ¶
7 years ago
When using if statements without the curly braces, remember than only one statement will be executed as part of that condition. If you want to place multiple statements you must use curly braces, and not just put them on the same line.
<?php
if (1==0) echo "Test 1."; echo "Test 2";
?>
Whereas some people would expect nothing to be displayed, this piece of code will show: "Test 2".
austinderrick2 at gmail dot com ¶
8 years ago
As an added note to the guy below, in such a case, use the !== operator like this.
$nkey = array_search($needle, $haystack);
if ($nkey !== false) { ...
The !== and the === compare the "types". So, with this type of comparision, 0 is not the same as the FALSE returned by the array_search array when it can not find a match. :)
Quoted Text:
===================================
Be careful with stuff like
if ($nkey = array_search($needle, $haystack)) { ...
if the returned key is actually the key 0, then the if won't be executed
===================================
redrobinuk at aol dot com ¶
10 years ago
This is aimed at PHP beginners but many of us do this Ocasionally...
When writing an if statement that compares two values, remember not to use a single = statement.
eg:
<?php
if ($a = $b)
{
print("something");
}
?>
This will assign $a the value $b and output the statement.
To see if $a is exactly equal to $b (value not type) It should be:
<?php
if ($a == $b)
{
print("something");
}
?>
Simple stuff but it can cause havok deep in classes/functions etc...
sofwan at sofwan dot net ¶
6 years ago
It seems that only numbers can be compared between them but actually an alphabet can be compare too. For example :
<?php
// Number comparison
$a="C";
$b="X";
if ($a<$b)
{
echo $a."is smaller than".$b;
}
// Result : C is smaller than X
?>
john ¶
9 years ago
@henryk (and everybody):
You should put your arguments in order by *least* likely to be true. That way if php is going to be able to quit checking, it will happen sooner rather than later, and your script will run (what amounts to unnoticeably) faster.
At least, that makes the most sense to me, but I don't claim omniscience.
contact at bsorin dot romania ¶
9 years ago
This has got the better part of my last 2 hours, so I'm putting it here, maybe it will save someone some time.
I had a
if (function1() && function2())
statement. Before returning true or false, function1() and function2() had to output some text. The trick is that, if function1() returns false, function2() is not called at all. It seems I should have known that, but it slipped my mind.
Anonymous ¶
9 years ago
Re : henryk dot kwak at gmail dot com
<?php function message($m)
{
echo "$m <br />\r";
return true;
}
$k=false;
if (message("first")&& $k && message("second")){;}
// will show
//first
class
$k=true;
if (message("first")&& $k && message("second")){;}
// will show
//first
//second
?>
Rudi ¶
7 years ago
Note that safe type checking (using === and !== instead of == and !=) is in general somewhat faster. When you're using non-safe type checking and a conversion is really needed for checking, safe type checking is considerably faster.
===================================
Test (100,000,000 runs):
<?php
$start = microtime(true);
for($i = 0; $i < 100000000; $i++)
if(5 == 10) {}
$end = microtime(true);
echo "1: ".($end - $start)."<br />\n";
unset($start, $end);
$start = microtime(true);
for($i = 0; $i < 100000000; $i++)
if('foobar' == 10) {}
$end = microtime(true);
echo "2: ".($end - $start)."<br />\n";
unset($start, $end);
$start = microtime(true);
for($i = 0; $i < 100000000; $i++)
if(5 === 10) {}
$end = microtime(true);
echo "3: ".($end - $start)."<br />\n";
unset($start, $end);
$start = microtime(true);
for($i = 0; $i < 100000000; $i++)
if('foobar' === 10) {}
$end = microtime(true);
echo "4: ".($end - $start)."<br />\n";
unset($start, $end);
?>
===================================
Result (depending on hardware configuration):
1: 16.779544115067
2: 21.305675029755
3: 16.345532178879
4: 15.991420030594
johovich at yandex dot ru ¶
9 months ago
'IF' STATEMENT WRONG BEHAVIOR
If assign var to function that returns 0 as integer or 0 as string 'if' statement condition works as false.
Test script:
---------------
//In this script you can see, that set var value to 0 is equal to boolean false
//applied to if statement. There is no diff between integer 0 or string '0'
if($pos = 0){
$pos++;
} else {
$pos = 0;
}
var_dump($pos);
//$pos is not boolean false, so it should do if condition true, but it's not
//to make this work well i use this
$pos = 0;
if($pos !== false){
$pos++;
} else {
$pos = 0;
}
var_dump($pos);
