note 124745 deleted from language.operators.precedence by cmb

Note Submitter: noone ---- Something that threw me of guard and I hadn't found it mentioned anywhere is if you're looking to asign a value in an if statement condition and use the same value in the said condition and compare it to a different value note the precedence of operators. if($a=5&&$a==5){ echo '5'; } else { echo 'not 5'; } //echos not 5 You'll get a Notice: Undefined variable: a; This happens because the expression is treated as ($a=5&&($a==5)) In this case $a was undefined. Use parentheses to enforce the desired outcome or and instead of &&. if(($a=5)&&$a==5){ // or $a=5 and $a==5 echo '5'; } else { echo 'not 5'; } //echos 5 We get no notice! A use case for this can be a three part condition that first checks if a value is valid, second assigns a new variable based on the first value and then checks if the result is valid. $ID=100; if ($ID&&($data=get_table_row_for_ID($ID))&&$data->is_valid()) { //NOTE: assigned $data // do something with the data } If assigning variables in an if condition I recommend adding a comment at the end of the line that such an action took place.