codexpower Posted January 31, 2015 Share Posted January 31, 2015 What I remember from my college days is that isset check whether the variable has a value set or not and return true or false value. However I encountered a code in wordpress - // Set up the content width value based on the theme's design and stylesheet. if ( ! isset( $content_width ) ) $content_width = 625; Here why is this sign used ! This sign is actually not equal to, Right? Quote Link to comment Share on other sites More sharing options...
kicken Posted January 31, 2015 Share Posted January 31, 2015 ! is the operator for not. So !isset() reads as "not isset" or "is not set". That code sets $content_width to 625 if it has not already been defined. Quote Link to comment Share on other sites More sharing options...
jeffreyappel Posted February 27, 2015 Share Posted February 27, 2015 I would like to explain a bit more: ! is a NOT sign. Its a logical operator.you could place this before any test value to INVERT it. Here, in your text, isset will returns true if value is not set, other wise return false. Quote Link to comment Share on other sites More sharing options...
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