php 基础笔记

hmzone

　　/***************************bygarcon1986********************************/
　　<?php//php avancé 5 example$a = 'hello';$a .= 'world';$table =  'users';$id = 5;$sql = 'SELECT * FROM'.$table. "WHERE ID = '$id'";//date() G显示24小时的格式，i显示分钟echo 'il est'.date('G /h i').'il fait beau<p>';// '=', '==', '===' 三者区别: '='是赋值，右边的值赋给左边；'=='是值相等，类型不一定等；'==='是恒等，值相等类型也相等；'!=='是值不等，或类型不等。$a = '34';$b = 34;$a == $b;//echo (boolean)($a == $b);var_dump((bool) $a == $b);echo '<br>';$a === $b;//echo (boolean)($a === $b);var_dump((bool) $a === $b);echo '<br>';var_dump((bool)($a !== $b));echo '<p>';//arithmetic operatorecho 5*"", '<br>'; //0echo 5+false, '<br>'; //5echo 5/NULL, '<br>'; //Warning: Division by zero//assignment operator$a = ($b = 4) + 5; // $a 现在成了 9，而 $b 成了 4。echo "$a,$b<br>";$a = 3;$a += 5; // sets $a to 8, as if we had said: $a = $a + 5;$b = "Hello ";$b .= "There!"; // sets $b to "Hello There!", just like $b = $b . "There!";echo "$a,$b<br>";//bitwise operatorecho 12 ^ 9; // 输出为 '5'echo '<br>';echo "12" ^ "9"; // 输出退格字符（ascii 8）// ('1' (ascii 49)) ^ ('9' (ascii 57)) = #8echo '<br>';echo "hallo" ^ "hello"; // 输出 ascii 值 #0 #4 #0 #0 #0echo '<p>';                            // 'a' ^ 'e' = #4/*---------     ---------  -- ---------result        value      op test---------     ---------  -- ---------Bitwise AND( 0 = 0000) = ( 0 = 0000) & ( 5 = 0101)( 1 = 0001) = ( 1 = 0001) & ( 5 = 0101)( 0 = 0000) = ( 2 = 0010) & ( 5 = 0101)( 4 = 0100) = ( 4 = 0100) & ( 5 = 0101)( 0 = 0000) = ( 8 = 1000) & ( 5 = 0101)Bitwise Inclusive OR( 5 = 0101) = ( 0 = 0000) | ( 5 = 0101)( 5 = 0101) = ( 1 = 0001) | ( 5 = 0101)( 7 = 0111) = ( 2 = 0010) | ( 5 = 0101)( 5 = 0101) = ( 4 = 0100) | ( 5 = 0101)(13 = 1101) = ( 8 = 1000) | ( 5 = 0101)Bitwise Exclusive OR (XOR)( 5 = 0101) = ( 0 = 0000) ^ ( 5 = 0101)( 4 = 0100) = ( 1 = 0001) ^ ( 5 = 0101)( 7 = 0111) = ( 2 = 0010) ^ ( 5 = 0101)( 1 = 0001) = ( 4 = 0100) ^ ( 5 = 0101)(13 = 1101) = ( 8 = 1000) ^ ( 5 = 0101)*///comparison operatorvar_dump(0 == "a"); // 0 == 0 -> trueecho '<br>';var_dump("1" == "01"); // 1 == 1 -> trueecho '<br>';var_dump("1" == "1e0"); // 1 == 1 -> trueecho '<br>';switch ("a") {case 0:echo "0";break;case "a": // never reached because "a" is already matched with 0echo "a";break;}echo '<p>';//error control operator//execution operator$output =`ls -al`;echo "<pre>$output</pre>";//increment-decrement operator$i = 'W';for ($n=0; $n<6; $n++) {echo ++$i . "/n";}echo "<h3>Postincrement</h3>";$a = 5;echo "Should be 5: " . $a++ . "<br />/n";echo "Should be 6: " . $a . "<br />/n";echo "<h3>Preincrement</h3>";$a = 5;echo "Should be 6: " . ++$a . "<br />/n";echo "Should be 6: " . $a . "<br />/n";echo "<h3>Postdecrement</h3>";$a = 5;echo "Should be 5: " . $a-- . "<br />/n";echo "Should be 4: " . $a . "<br />/n";echo "<h3>Predecrement</h3>";$a = 5;echo "Should be 4: " . --$a . "<br />/n";echo "Should be 4: " . $a . "<br />/n";//array operators//type operatorsclass MyClass{}class NotMyClass{}$a = new MyClass;var_dump($a instanceof MyClass);var_dump($a instanceof NotMyClass);?>