How does true false work in PHP

Question

I wonder how PHP handles true false comparison internally   I understand that true is defined as 1 and false is defined as 0   When I do if  a    echo  true    it echos  true   How does PHP recognize  a  as 1

User · Answer

think of operator as unary function  is false type value  which returns true or false  depending on the exact implementation for specific type and value   Consider if statement to invoke such function implicitly  via syntactic sugar   other possibility is that type has cast operator  which turns type into another type implicitly  in this case string to Boolean   PHP does not expose such details  but C   allows operator overloading which exposes fine details of operator implementation

User · Answer

Since I ve visited this page several times  I ve decided to post an example  loose  comparison test   Results             - gt  false  0        - gt  false  1        - gt  true  01       - gt  true  abc      - gt  true  true     - gt  true  false    - gt  true 0         - gt  false 0 1       - gt  true 1         - gt  true 1 1       - gt  true -42       - gt  true  NAN      - gt  true 0         - gt  false           - gt  true null      - gt  false true      - gt  true false     - gt  false           - gt  false   a       - gt  true           - gt  true           - gt  true   s   f   - gt  true   Code   class Vegetable     class Fruit       public  s    f       cases                  0        1        01        abc        true        false       0      0 1      1      1 1      -42       NAN        float   NAN       NAN      null      true      false                a        new stdClass        new Vegetable        new Fruit        echo   lt pre gt     PHP EOL   foreach   cases as  case        printf   s - gt   s    PHP EOL  str pad json encode  case   9       STR PAD RIGHT   json encode   case    true         When a strict       comparison is done  everything except true returns false

User · Answer

The best operator for strict checking is  if  foo     true      That way  you re really checking if its true  and not 1 or simply just set

User · Answer

PHP uses weak typing  which it calls  type juggling    which is a bad idea  though that s a conversation for another time    When you try to use a variable in a context that requires a boolean  it will convert whatever your variable is into a boolean  according to some mostly arbitrary rules available here  http   www php net manual en language types boolean php language types boolean casting

User · Answer

Zero is false  nonzero is true    In php you can test more explicitly using the     operator    if  0  false       echo  works      will echo works  if  0   false       echo  works      will not echo anything

User · Answer

This is covered in the PHP documentation for booleans and type comparison tables   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   Every other value is considered TRUE

[php] How does true/false work in PHP?

Examples related to php