目錄
[1]條件語句 if語句 switch語句 [2]循環(huán)語句 while循環(huán) do…while循環(huán) for循環(huán) foreach循環(huán)條件語句
用于基于不同條件執(zhí)行不同的動作
if語句
<span style="color: #0000ff;">if</span><span style="color: #000000;"> (條件) { 當(dāng)條件為 </span><span style="color: #0000ff;">true</span><span style="color: #000000;"> 時執(zhí)行的代碼;}</span>
<span style="color: #0000ff;">if</span><span style="color: #000000;"> (條件) { 條件為 </span><span style="color: #0000ff;">true</span><span style="color: #000000;"> 時執(zhí)行的代碼;} </span><span style="color: #0000ff;">else</span><span style="color: #000000;"> { 條件為 </span><span style="color: #0000ff;">false</span><span style="color: #000000;"> 時執(zhí)行的代碼;}</span>
<span style="color: #0000ff;">if</span><span style="color: #000000;"> (條件) { 條件為 </span><span style="color: #0000ff;">true</span><span style="color: #000000;"> 時執(zhí)行的代碼;} elseif (條件) { 條件為 </span><span style="color: #0000ff;">true</span><span style="color: #000000;"> 時執(zhí)行的代碼;} </span><span style="color: #0000ff;">else</span><span style="color: #000000;"> { 條件為 </span><span style="color: #0000ff;">false</span><span style="color: #000000;"> 時執(zhí)行的代碼;}</span>
<span style="color: #000000;">php</span><span style="color: #800080;">$t</span>=<span style="color: #008080;">date</span>("H"<span style="color: #000000;">);</span><span style="color: #0000ff;">if</span> (<span style="color: #800080;">$t</span>) { <span style="color: #0000ff;">echo</span> "Have a good morning!"<span style="color: #000000;">;} </span><span style="color: #0000ff;">elseif</span> (<span style="color: #800080;">$t</span>) { <span style="color: #0000ff;">echo</span> "Have a good day!"<span style="color: #000000;">;} </span><span style="color: #0000ff;">else</span><span style="color: #000000;"> { </span><span style="color: #0000ff;">echo</span> "Have a good night!"<span style="color: #000000;">;}</span>?>
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switch語句
<span style="color: #0000ff;">switch</span><span style="color: #000000;"> (expression){</span><span style="color: #0000ff;">case</span> label1:<span style="color: #000000;"> code to be executed </span><span style="color: #0000ff;">if</span> expression =<span style="color: #000000;"> label1; </span><span style="color: #0000ff;">break</span><span style="color: #000000;">; </span><span style="color: #0000ff;">case</span> label2:<span style="color: #000000;"> code to be executed </span><span style="color: #0000ff;">if</span> expression =<span style="color: #000000;"> label2; </span><span style="color: #0000ff;">break</span><span style="color: #000000;">;</span><span style="color: #0000ff;">default</span>:<span style="color: #000000;"> code to be executed </span><span style="color: #0000ff;">if</span><span style="color: #000000;"> expression is different from both label1 and label2;}</span>
<span style="color: #000000;">php</span><span style="color: #0000ff;">switch</span> (<span style="color: #800080;">$x</span><span style="color: #000000;">){</span><span style="color: #0000ff;">case</span> 1: <span style="color: #0000ff;">echo</span> "Number 1"<span style="color: #000000;">; </span><span style="color: #0000ff;">break</span><span style="color: #000000;">;</span><span style="color: #0000ff;">case</span> 2: <span style="color: #0000ff;">echo</span> "Number 2"<span style="color: #000000;">; </span><span style="color: #0000ff;">break</span><span style="color: #000000;">;</span><span style="color: #0000ff;">case</span> 3: <span style="color: #0000ff;">echo</span> "Number 3"<span style="color: #000000;">; </span><span style="color: #0000ff;">break</span><span style="color: #000000;">;</span><span style="color: #0000ff;">default</span>: <span style="color: #0000ff;">echo</span> "No number between 1 and 3"<span style="color: #000000;">;}</span>?>
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循環(huán)語句
在編寫代碼時，經(jīng)常需要反復(fù)運(yùn)行同一代碼塊，可以使用循環(huán)來執(zhí)行這樣的任務(wù)
while循環(huán)
<span style="color: #0000ff;">while</span><span style="color: #000000;"> (條件為真) { 要執(zhí)行的代碼;}</span>
<span style="color: #000000;">php</span><span style="color: #800080;">$sum</span> = 12;<span style="color: #008000;">//</span><span style="color: #008000;">小寵物當(dāng)前的饑餓程度</span><span style="color: #0000ff;">echo</span> "我餓啦:-("<span style="color: #000000;">;</span><span style="color: #0000ff;">echo</span> "<br>"<span style="color: #000000;">;</span><span style="color: #0000ff;">while</span>(<span style="color: #800080;">$sum</span>){<span style="color: #008000;">//</span><span style="color: #008000;">小寵物的饑餓程度到100，表示小寵物吃飽啦,不用繼續(xù)喂了，沒吃飽繼續(xù)喂食</span> <span style="color: #800080;">$num</span> = <span style="color: #008080;">rand</span>(1,20);<span style="color: #008000;">//</span><span style="color: #008000;">隨機(jī)數(shù)，模擬喂食小寵物的小面包</span> <span style="color: #800080;">$sum</span> = <span style="color: #800080;">$sum</span> + <span style="color: #800080;">$num</span>; <span style="color: #008000;">//</span><span style="color: #008000;">小寵物吃小面包</span> <span style="color: #0000ff;">echo</span> "我還沒吃飽呢！"<span style="color: #000000;">; </span><span style="color: #0000ff;">echo</span> "<br>"<span style="color: #000000;">;}</span><span style="color: #0000ff;">echo</span> "終于吃飽啦^_^"<span style="color: #000000;">;</span>?>
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do…while循環(huán)
循環(huán)首先會執(zhí)行一次代碼塊，然后檢查條件，如果指定條件為真，則重復(fù)循環(huán)
<span style="color: #0000ff;">do</span><span style="color: #000000;"> { 要執(zhí)行的代碼;} </span><span style="color: #0000ff;">while</span> (條件為真);
<span style="color: #000000;">php </span><span style="color: #800080;">$sum</span> = 0<span style="color: #000000;">; </span><span style="color: #0000ff;">do</span><span style="color: #000000;">{ </span><span style="color: #800080;">$num</span> = <span style="color: #008080;">rand</span>(1,6);<span style="color: #008000;">//</span><span style="color: #008000;">獲取1至6的隨機(jī)數(shù)，模擬擲骰子</span> <span style="color: #800080;">$sum</span> = <span style="color: #800080;">$sum</span> + <span style="color: #800080;">$num</span>;<span style="color: #008000;">//</span><span style="color: #008000;">前進(jìn)步長</span> }<span style="color: #0000ff;">while</span>(<span style="color: #800080;">$num</span>==6<span style="color: #000000;">); </span><span style="color: #0000ff;">echo</span> "do...while例子執(zhí)行完畢，前進(jìn)：".<span style="color: #800080;">$sum</span> ."<br>"<span style="color: #000000;">;</span>?>
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for循環(huán)
for循環(huán)語句中，初始化在循環(huán)開始前無條件求值一次，循環(huán)條件在每次循環(huán)開始前求值。如果值為true，則繼續(xù)循環(huán)，執(zhí)行循環(huán)體語句；如果值為false,則終止循環(huán)。遞增語句在每次循環(huán)后執(zhí)行
<span style="color: #0000ff;">for</span><span style="color: #000000;"> (init counter; test counter; increment counter) { code to be executed;} </span>
<span style="color: #000000;">php </span><span style="color: #0000ff;">for</span> (<span style="color: #800080;">$x</span>=0; <span style="color: #800080;">$x</span>$x++<span style="color: #000000;">) { </span><span style="color: #0000ff;">echo</span> "數(shù)字是：<span style="color: #800080;">$x</span> <br>"<span style="color: #000000;">;} </span>?>
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foreach循環(huán)
foreach循環(huán)只適用于數(shù)組，用于遍歷數(shù)組中每個鍵/值對。每進(jìn)行一次循環(huán)迭代，當(dāng)前數(shù)組元素的值就會被賦值給$value變量，并且數(shù)組指針會逐一移動，直到到達(dá)最后一個數(shù)組元素。一般有兩種方式：不取下標(biāo)、取下標(biāo)
[1]只取值，不取下標(biāo)
<span style="color: #0000ff;">foreach</span> (<span style="color: #800080;">$array</span> <span style="color: #0000ff;">as</span> <span style="color: #800080;">$value</span><span style="color: #000000;">) { code to be executed;} </span>
<span style="color: #000000;">php </span><span style="color: #800080;">$colors</span> = <span style="color: #0000ff;">array</span>("red","green","blue","yellow"<span style="color: #000000;">); </span><span style="color: #0000ff;">foreach</span> (<span style="color: #800080;">$colors</span> <span style="color: #0000ff;">as</span> <span style="color: #800080;">$value</span><span style="color: #000000;">) { </span><span style="color: #0000ff;">echo</span> "<span style="color: #800080;">$value</span> <br>"<span style="color: #000000;">;}</span>?>
[2]同時取下標(biāo)和值
<span style="color: #0000ff;">foreach</span> (<span style="color: #800080;">$array</span> <span style="color: #0000ff;">as</span> <span style="color: #800080;">$index</span> => <span style="color: #800080;">$value</span><span style="color: #000000;">) { code to be executed;} </span>
<span style="color: #000000;">php </span><span style="color: #800080;">$colors</span> = <span style="color: #0000ff;">array</span><span style="color: #000000;">( </span>"r"=>"red", "g"=>"green", "b"=>"blue", "y"=>"yellow"<span style="color: #000000;">); </span><span style="color: #0000ff;">foreach</span> (<span style="color: #800080;">$colors</span> <span style="color: #0000ff;">as</span> <span style="color: #800080;">$key</span> => <span style="color: #800080;">$value</span><span style="color: #000000;">) { </span><span style="color: #0000ff;">echo</span> <span style="color: #800080;">$key</span>.":".<span style="color: #800080;">$value</span>."<br>"<span style="color: #000000;">;}</span>?>
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