案例：php案例     状态：不可编辑再运行    进入竖版
 运行结果　
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<!DOCTYPE html>
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<html>
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<body>
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​
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<?php
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$arr = array("blue","red","green","yellow");
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print_r(str_replace("red","pink",$arr,$i));
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echo "替换数：$i";
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?>
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</body>
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</html>
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​
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