??是PHP7版本的新特性,它与?:的区别在哪里呢?
??
$b = $a?? $c ;相当于$b= isset($a)?$a:$c;
?:
$b = $a?$a: $c 则是 $b = !empty($a) ? $a:$c;
');mask-image:url('data:image/svg+xml;utf8,');mask-mode:alpha;-webkit-mask-repeat:no-repeat;mask-repeat:no-repeat;-webkit-mask-size:contain;mask-size:contain;-webkit-mask-position:center;mask-position:center;border-radius:0}}.wp-block-image :where(.has-border-color){border-style:solid}.wp-block-image :where([style*=border-top-color]){border-top-style:solid}.wp-block-image :where([style*=border-right-color]){border-right-style:solid}.wp-block-image :where([style*=border-bottom-color]){border-bottom-style:solid}.wp-block-image :where([style*=border-left-color]){border-left-style:solid}.wp-block-image :where([style*=border-width]){border-style:solid}.wp-block-image :where([style*=border-top-width]){border-top-style:solid}.wp-block-image :where([style*=border-right-width]){border-right-style:solid}.wp-block-image :where([style*=border-bottom-width]){border-bottom-style:solid}.wp-block-image :where([style*=border-left-width]){border-left-style:solid}.wp-block-image figure{margin:0}/*]]>*/
??是PHP7版本的新特性,它与?:的区别在哪里呢?
$b = $a?? $c ;相当于$b= isset($a)?$a:$c;
$b = $a?$a: $c 则是 $b = !empty($a) ? $a:$c;
作者:
标签