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The
if
construct is one of the most important
features of many languages, PHP included. It allows for
conditional execution of code fragments. PHP features an
if
structure that is similar to that of C:
if (expr)
statement
As described in
the section about
expressions
,
expression
is evaluated to its
Boolean value. If
expression
evaluates to
true
,
PHP will execute
statement
, and if it evaluates
to
false
- it'll ignore it. More information about what values evaluate
to
false
can be found in the
'Converting to boolean'
section.
The following example would display
a is bigger
than b
if
$a
is bigger
than
$b
:
<?php
if (
$a
>
$b
)
echo
"a is bigger than b"
;
?>
Often you'd want to have more than one statement to be executed
conditionally. Of course, there's no need to wrap each statement
with an
if
clause. Instead, you can group
several statements into a statement group. For example, this code
would display
a is bigger than b
if
$a
is bigger than
$b
, and would then assign the value of
$a
into
$b
:
<?php
if (
$a
>
$b
) {
echo
"a is bigger than b"
;
$b
=
$a
;
}
?>
If
statements can be nested infinitely within other
if
statements, which provides you with complete
flexibility for conditional execution of the various parts of your
program.
＋
add a note
User Contributed Notes
7 notes
robk
¶
10 years ago
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
?>
techguy14 at gmail dot com
¶
12 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
) {
}
}
}
?>
You could just simply do this:
<?php
if( (
$a
==
1
||
$a
==
2
) && (
$b
==
3
||
$b
==
4
) && (
$c
==
5
||
$c
==
6
) ) {
}
?>
Hope this helps!
Christian L.
¶
12 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
= (
3
==
$v
) ?
'Yes'
:
'No'
;
echo (
1
==
$v
) ?
'Yes'
:
'No'
;
$v
=
'My Value'
;
$r
= (
$v
) ?:
'No Value'
;
$v
=
''
;
echo (
$v
) ?:
'No Value'
;
?>
Parentheses can be left out in all examples above.
cole dot trumbo at nospamthnx dot gmail dot com
¶
6 years 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
;
?>
chiel at comfitech dot nl
¶
7 months ago
Note that the IF statement does not always evaluates all expressions. In the next example the second expression will not be evaluated causing our function not to run. Because the result is already TRUE and the rest of the expressions are behind the OR operator they will be ignored.
<?php
$a
=
0
;
if (
true
||
$a
=
important_function
() ) echo
$a
;
function
important_function
(){
return
1
;
}
?>
