The if statement doesn't work for false in php - php

Question

When trying to get familiar with if statement in PHP, this happened.
First time i tried this code below.
if(true) {echo 'true';} else {echo 'false';}
And the output was true when the condition is true. Again, when the condition is false (if(false)) it echos false.
But i tried the same, using a variable as the condition, while changing the value of the variable.
$con='false';
if($con){echo 'true';} else{echo 'false';}
At this situation the output is true even when the variable value is false or true. At the same time, the if statement working fine when 1 and 0 is used instead true and false. Why is this happening?

Answer 1

$con='false';
That 'false' is a valid string which is not Boolean FALSE, just like $con='hi'; isn't.
$con=FALSE; //this is false now
To quote from the Manual
To specify a boolean literal, use the constants TRUE or FALSE. Both are case-insensitive.
Also read these other options that you have
When converting to boolean, the following values are considered FALSE:
◦ the boolean FALSE itself
◦ the integer 0 (zero)
◦ the float 0.0 (zero)
◦ the empty string, and the string "0"
◦ an array with zero elements
◦ an object with zero member variables (PHP 4 only)
◦ the special type NULL (including unset variables)
◦ SimpleXML objects created from empty tags
Then you observed this
At the same time, the if statement working fine when 1 and 0 is used instead true and false. Why is this happening?
This is because 0 in any form is FALSE, either string or numeric. But the text false as a string is not false for reasons mentioned above.
Also read about PHP Strict Comparisons since you're learning, because
var_dump(0==FALSE); //bool(true)
var_dump(0===FALSE); //bool(false) :)

Answer 2

PHP does some sneaky things in the if expression. The following values are considered FALSE:
the boolean FALSE itself
the integer 0 (zero)
the float 0.0 (zero)
the empty string, and the string "0"
an array with zero elements
an object with zero member variables (PHP 4 only)
the special type NULL (including unset variables)
SimpleXML objects created from empty tags
Every other value is considered TRUE (including any resource).
You're actually passing a string that says the word false, rather than the value false itself. Because that isn't in the above list, it is actually considered true!

Answer 3

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.
So as per docs try using
$con = false;//boolean and not a string
if($con){echo 'true';} else{echo 'false';}
When converting to boolean, the following values are considered FALSE:
◦ the boolean FALSE itself
◦ the integer 0 (zero)
◦ the float 0.0 (zero)
◦ the empty string, and the string "0"
◦ an array with zero elements
◦ an object with zero member variables (PHP 4 only)
◦ the special type NULL (including unset variables)
◦ SimpleXML objects created from empty tags
Check Docs (IF MANUAL)

Answer 4

You are using 'false' as a STRING variable, but that is the WORD false, not the BOOLEAN constant. Just use false
if(true) {echo 'true';} else {echo 'false';}
$con='false'; // Wrong
$con=false; // Right
if($con){echo 'true';} else{echo 'false';}
And when you are doing if statements, this will work:
if ($con == false) { echo 'false'; }
or you can use a === which compares one expression to another by value and by type.
if ($con === false) { echo 'false with type safe comparison!'; }

Answer 5

Use a bool instead of a string:
$con = false;
Your if statement will simply check that $con is not empty, so in your example it will always be true.

Answer 6

You can assign value to variable like this
$con=false;

Answer 7

In your second example, $con isn't the boolean false, it's a string literal 'false' (note the quotes), and any non-empty string in PHP evaluates as true.
To fix this, just drop the quotes:
$con=false; // no quotes!
if($con){echo 'true';} else{echo 'false';}

Answer 8

Your $con declaration is a string not a bool. So it will always return true.
To declare a boolean, use:
$con=FALSE; //or TRUE

Answer 9

'false' is not same as false.
if('true') or if('false') will result true always as they will be treated as strings and will be converted for comparison.
$con=false;
if($con){echo 'true';} else{echo 'false';}
Will print false

Answer 10

change the value of your variable to this
$con = false;