PHP开发实战权威指南,php实战指南
3.2.1 变量的声明与命名
<span> 1</span> <?<span>php </span><span> 2</span> <span>$title</span>="hello"; <span>//</span><span>正确</span> <span> 3</span> <span>$title123</span>="hello"; <span>//</span><span>正确</span> <span> 4</span> $123title="hello"; <span>//</span><span>错误</span> <span> 5</span> <span>$_title</span>="hello"; <span>//</span><span>正确</span> <span> 6</span> $@<span>#</span><span>title="hello"; //错误</span> <span> 7</span> <span>$url</span>="hello"; <span>//</span><span>我们得到一个变量url</span> <span> 8</span> <span>echo</span> <span>$url</span>; <span>//</span><span>结果:hello</span> <span> 9</span> <span>unset</span>(<span>$url</span>); <span>//</span><span>删除一个变量url</span> <span>10</span> <span>echo</span> <span>$url</span>; <span>//</span><span>结果为空</span> <span>11</span> ?>
3.2.2 可变变量与引用赋值
<span>1</span> <?<span>php </span><span>2</span> <span>$var</span>="php"<span>; </span><span>3</span> <span>$php</span>="hello"<span>; </span><span>4</span> <span>echo</span> <span>$var</span>; <span>//</span><span>输出结果php</span> <span>5</span> <span>echo</span> $<span>$var</span>; <span>//</span><span>输出结果hello</span> <span>6</span> ?>
3.3.1 字符串
<span>1</span> <?<span>php </span><span>2</span> <span>$title</span>="hello"<span>; </span><span>3</span> <span>echo</span> '$title,world'; <span>//</span><span>结果:$title,world</span> <span>4</span> <span>echo</span> "<span>$title</span>,world "; <span>//</span><span>结果:hello,world</span> <span>5</span> <span>echo</span> "${title},world"; <span>//</span><span>结果:hello,world</span> <span>6</span> <span>echo</span> "{<span>$title</span>},world"; <span>//</span><span>结果:hello,world</span> <span>7</span> <span>echo</span> "\$title,world"; <span>//</span><span>结果:$title,world</span> <span>8</span> ?>
3.3.8 类型的强制转换与应用
<span>//</span><span>其他类型转换成整型</span> <?<span>php </span><span>$php</span>=100.10<span>; </span><span>echo</span> (int)<span>$php</span>; <span>//</span><span>输出结果:100</span> <span>$php</span>=<span>true</span><span>; </span><span>echo</span> (int)<span>$php</span>; <span>//</span><span>输出结果:1</span> <span>$php</span>="123php"<span>; </span><span>echo</span> (int)<span>$php</span>; <span>//</span><span>输出结果:123</span> <span>$php</span>="php123"<span>; </span><span>echo</span> (int)<span>$php</span>; <span>//</span><span>输出结果:0</span> ?> <span>//</span><span>其他类型转化为字符串型</span> <?<span>php </span><span>$php</span>=100.1<span>; </span><span>var_dump</span>((<span>string</span>)<span>$php</span>); <span>//</span><span>输出结果:string(4)"100.1"</span> <span>$php</span>=<span>true</span><span>; </span><span>echo</span>(<span>string</span>)<span>$php</span>; <span>//</span><span>输出结果:1</span> ?> <span>//</span><span>其他类型转化为浮点型</span> <?<span>php </span><span>$php</span>="123.2php"<span>; </span><span>var_dump</span>((<span>float</span>)<span>$php</span>); <span>//</span><span>输出结果:float(123.2)</span> <span>$php</span>="php123.2"<span>; </span><span>var_dump</span>((<span>float</span>)<span>$php</span>); <span>//</span><span>输出结果:(0)</span> ?> <span>//</span><span>其他类型转化为布尔型</span> <?<span>php </span><span>$php</span>="php"<span>; </span><span>var_dump</span>((bool)<span>$php</span>); <span>//</span><span>输出结果:bool(true)</span> <span>$php</span>=0<span>; </span><span>var_dump</span>((bool)<span>$php</span>); <span>//</span><span>输出结果:bool(false)</span> ?>
《php和mysql web开发》
《php和mysql web开发》
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