php if and statement causing problems

Question

Im trying to test a validation using an if statement.

if (($red == "1") && ($blue = "1") ) { $green = "hello"; }

Before this statement runs $blue = 0.

After i run this... $blue changes to 1.

Any ideas why?

$blue++; ? is that what u want? correct = to == in second brackets — user1317647
– user1317647, Commented Apr 27, 2012 at 6:50
brian, edit your post to correct it. There's an "edit" link right below the tags. — Mat
– Mat, Commented Apr 27, 2012 at 6:50
Just read the code you posted once more, you should be able to find the mistake... — nplatis
– nplatis, Commented Apr 27, 2012 at 6:52
I seriously wonder though..., you managed to do it right for $red == "1" but not for $blue? — Andreas Wong
– Andreas Wong, Commented Apr 27, 2012 at 6:53

codaddict · Accepted Answer · 2012-04-27 06:55:37Z

6

You are using = in place of ==:

if (($red == "1") && ($blue = "1") ) { $green = "hello"; }
                           ^^^

As a result (assuming the left side of && returns true) $blue gets assigned "1".

It's one of the most common programming mistakes!! As a way to prevent it from happening programmers put the constant on the left hand side of the the == as:

1 == $blue

so that if by mistake you end up writing = in place of == :

1 = $blue

you get a syntax error as you cannot assign to a constant.

edited Apr 27, 2012 at 6:55

answered Apr 27, 2012 at 6:50

codaddict

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2 Comments

brian wilson Over a year ago

after so many hours i just couldn't see it! sometimes it takes someone else to see the simple. thanks

codaddict Over a year ago

@brianwilsonL: I've updated the answer with a tip to avoid such bugs.

Jobin · Accepted Answer · 2012-04-27 06:54:19Z

2

Try this if (($red == "1") && ($blue == "1") ) { $green = "hello"; }

//your code is ($blue ="1") '=' is an assignment operator in php comparison is '=='

answered Apr 27, 2012 at 6:54

Jobin

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Comments

vvr · Accepted Answer · 2012-04-27 06:53:31Z

1

you are assigning $blue = 1 instead of comparing that's why $blue is 1

answered Apr 27, 2012 at 6:53

vvr

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Comments

Florin Ghita · Accepted Answer · 2012-04-27 06:51:16Z

0

This is because you use =. Use $blue == "1".

answered Apr 27, 2012 at 6:51

Florin Ghita

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Comments

Shaikh Farooque · Accepted Answer · 2012-04-27 06:52:11Z

0

Your equal to sing is incorrect in next condistions if (($red == "1") && ($blue == "1") ) { $green = "hello"; }

answered Apr 27, 2012 at 6:52

Shaikh Farooque

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ehanoc · Accepted Answer · 2012-04-27 06:52:16Z

0

Yeah use == instead of =

I would go further and say that maybe you should put literals on the left hand when comparing to avoid such situations.

Like if(1 == $blue) instead of if($blue == 1)

answered Apr 27, 2012 at 6:52

ehanoc

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arun · Accepted Answer · 2012-04-27 06:57:21Z

0

use == or === instead of =.

the '=' is assignment operator, the conditional operators are == or ===

if (($red == "1") && ($blue == "1") ) 
 { 
     $green = "hello"; 
 }

answered Apr 27, 2012 at 6:57

arun

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