Logical Operators or OR

Question

I remember reading a while back in regards to logical operators that in the case of OR  using    was better than or  or vice versa    I just had to use this in my project when it came back to me  but I can t remember which operator was recommended or if it was even true   Which is better and why

User · Answer

I don t think one is inherently better than another one  but I would suggest sticking with    because it is the default in most languages   EDIT  As others have pointed out there is indeed a difference between the two

User · Answer

Source  http   wallstreetdeveloper com php-logical-operators   Here is sample code for working with logical operators    lt html gt    lt head gt       lt title gt Logical lt  title gt   lt  head gt    lt body gt       lt  php          a   10           b   20          if   a gt  b                        echo   A is Greater                     elseif   a lt  b                        echo   A is lesser                     else                        echo  A and B are equal                   gt       lt  php          c   30           d   40            if    a lt  c  AND   b lt  d           if    a lt  c   amp  amp    b lt  d                         echo  A and B are larger                     if  isset  d                d   100          echo  d          unset  d         gt       lt  php          var1   2          switch  var1                        case 1   echo  var1 is 1                        break              case 2   echo  var1 is 2                        break              case 3   echo  var1 is 3                        break              default  echo  var1 is unknown                   gt   lt  body gt   lt  html gt

User · Answer

There is nothing bad or better  It just depends on the precedence of operators  Since    has higher precedence than or  so    is mostly used

User · Answer

There is no  better  but the more common one is     They have different precedence and    would work like one would expect normally   See also  Logical operators  the following example is taken from there       The result of the expression  false    true  is assigned to  e    Acts like    e    false    true    e   false    true      The constant false is assigned to  f and then true is ignored    Acts like     f   false  or true   f   false or true

User · Answer

The difference between respectively    and OR and  amp  amp  and AND is operator precedence    bool   FALSE    TRUE   interpreted as   bool    FALSE    TRUE   value of  bool is TRUE    bool   FALSE OR TRUE   interpreted as    bool   FALSE  OR TRUE  value of  bool is FALSE    bool   TRUE  amp  amp  FALSE   interpreted as   bool    TRUE  amp  amp  FALSE   value of  bool is FALSE    bool   TRUE AND FALSE   interpreted as    bool   TRUE  AND FALSE  value of  bool is TRUE

User · Answer

Some languages use short-circuit  and others use full Boolean evaluation  if you know  this is similar to the directive  B in Pascal    Explanations   function A           Do something       return true     function B           Do something       return true     if   A   OR B               In this example the function B   will never be executed  Since the function A   returns TRUE  the result of the OR statement is known from the first part without it being necessary to evaluate the second part of the expression   However with   A      B      the second part is always evaluated regardless of the value of the first   For optimized programming  you should always use OR which is faster  except for the case when the first part returns false and second part actually needs to be evaluated

User · Answer

I know it s an old topic but still  I ve just met the problem in the code I am debugging at work and maybe somebody may have similar issue     Let s say the code looks like this    positions    this- gt positions            You would expect  as you are used to from e g  javascript  that when  this- positions   returns false or null   positions is empty array  But it isn t  The value is TRUE or FALSE depends on what  this- positions   returns    If you need to get value of  this- positions   or empty array  you have to use    positions    this- gt positions   or         EDIT   The above example doesn t work as intended but the truth is that    and or is not the same    Try this    lt  php  function returnEmpty         return  string       return  1     return null      first   returnEmpty           second   returnEmpty   or      third   returnEmpty           var dump  first   var dump  second   var dump  third   echo   n     This is the result   bool false  NULL array 0        So  actually the third option    is the correct solution when you want to set returned value or empty array    positions    this- gt positions            Tested with PHP 7 2 1

User · Answer

They are used for different purposes and in fact have different operator precedences   The  amp  amp  and    operators are intended for Boolean conditions  whereas and and or are intended for control flow   For example  the following is a Boolean condition   if   foo     bar  amp  amp   baz     quxx      This differs from control flow   doSomething   or die

[php] Logical Operators, || or OR?

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