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xiexie 发表于 2020-12-7 14:44

PHP7空合并运算符如何使用

<p style="margin-bottom: 5px; color: rgb(51, 51, 51); line-height: 1.7; font-family: -apple-system, BlinkMacSystemFont, " helvetica="" neue",="" "pingfang="" sc",="" "microsoft="" yahei",="" "source="" han="" sans="" "noto="" cjk="" "wenquanyi="" micro="" hei",="" sans-serif;="" font-size:="" 15px;"="">在 PHP7 中,引入了一个新的功能,即空合并运算符(??)。由于在 PHP7 项目中存在大量同时使用三元表达式和 isset() 的情况,因此新增的空合并运算符可以用来取代三元运算与 isset () 函数,如果变量是存在的并且不为 null ,则空合并运算符将返回它的第一个操作数;否则将返回其第二个操作数。<br style="margin: 0px; padding: 0px;"></p><p style="margin-bottom: 5px; color: rgb(51, 51, 51); line-height: 1.7; font-family: -apple-system, BlinkMacSystemFont, " helvetica="" neue",="" "pingfang="" sc",="" "microsoft="" yahei",="" "source="" han="" sans="" "noto="" cjk="" "wenquanyi="" micro="" hei",="" sans-serif;="" font-size:="" 15px;"="">在旧版的PHP中:isset($_GET[‘id']) ? $_GET[id] : err;而新版的写法为:$_GET['id'] ?? 'err';</p><p style="margin-bottom: 5px; color: rgb(51, 51, 51); line-height: 1.7; font-family: -apple-system, BlinkMacSystemFont, " helvetica="" neue",="" "pingfang="" sc",="" "microsoft="" yahei",="" "source="" han="" sans="" "noto="" cjk="" "wenquanyi="" micro="" hei",="" sans-serif;="" font-size:="" 15px;"=""><br></p><p style="margin-bottom: 5px; color: rgb(51, 51, 51); line-height: 1.7; font-family: -apple-system, BlinkMacSystemFont, " helvetica="" neue",="" "pingfang="" sc",="" "microsoft="" yahei",="" "source="" han="" sans="" "noto="" cjk="" "wenquanyi="" micro="" hei",="" sans-serif;="" font-size:="" 15px;"="">样例:</p><p style="margin-bottom: 5px; line-height: 1.7;"><font color="#333333" face="-apple-system, BlinkMacSystemFont, Helvetica Neue, PingFang SC, Microsoft YaHei, Source Han Sans SC, Noto Sans CJK SC, WenQuanYi Micro Hei, sans-serif"><span style="font-size: 15px;">echo $_GET['CODE']??'error';</span></font></p><p style="margin-bottom: 5px; line-height: 1.7;"><font color="#333333" face="-apple-system, BlinkMacSystemFont, Helvetica Neue, PingFang SC, Microsoft YaHei, Source Han Sans SC, Noto Sans CJK SC, WenQuanYi Micro Hei, sans-serif"><span style="font-size: 15px;"><br></span></font></p><p style="margin-bottom: 5px; line-height: 1.7;"><font color="#333333" face="-apple-system, BlinkMacSystemFont, Helvetica Neue, PingFang SC, Microsoft YaHei, Source Han Sans SC, Noto Sans CJK SC, WenQuanYi Micro Hei, sans-serif"><span style="font-size: 15px;">输出:</span></font></p><p style="margin-bottom: 5px; line-height: 1.7;"><font color="#333333" face="-apple-system, BlinkMacSystemFont, Helvetica Neue, PingFang SC, Microsoft YaHei, Source Han Sans SC, Noto Sans CJK SC, WenQuanYi Micro Hei, sans-serif"><span style="font-size: 15px;">error</span></font></p>

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