The similarities and differences between & and && in PHP logic operators

PHP has 5 arithmetic operators (+-*/%), 6 assignment operators (+ = = *=/=%=. =), 8 comparison operators (= = = < > <= >=! = <>!==), and 6 logical operators (such as &&, | |, &, |,!. Where logic and & can be written and, logically or | written or, and some other operators (error control operator @, execute operator anti-quote "-not single quotes, string operators.) ++/--、 ternary operator with. =, increment/decrement operator?:).

For operator Precedence, refer to the relevant documentation.

The similarities and differences between & and && in PHP

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2. <?php
4. $a = 10;
6. if ($a >4 && (+$a >10))
8. {
10. }
12. The output result is 11.
14. echo $a;
16. ?>
20. <?php
22. $a = 10;
24. if ($a >4 and (+$a >10))
26. {
28. }
30. The output result is 11.
32. echo $a;
34. ?>
38. **************************************************************
42. <?php
44. $a = 10;
46. if ($a >4 && (+$a <10))
48. {
50. }
52. The output result is 11.
54. echo $a;
56. ?>
60. <?php
62. $a = 10;
64. if ($a >4 & (+$a <10))
66. {
68. }
70. The output result is 11.
72. echo $a;
74. ?>
78. *********************************************************
82. <?php
84. $a = 10;
86. if ($a <4 && (+$a >10))
88. {
90. }
92. The output result is 10.
94. echo $a;
96. ?>
100. <?php
102. $a = 10;
104. if ($a <4 & (+$a >10))
106. {
108. }
110. The output result is 11.
112. echo $a;
114. ?>
118. *******************************************************************
122. <?php
124. $a = 10;
126. if ($a <4 && (+$a <10))
128. {
130. }
132. The output result is 10.
134. echo $a;
136. ?>
140. <?php
142. $a = 10;
144. if ($a <4 & (+$a <10))
146. {
148. }
150. The output result is 11.
152. echo $a;
154. ?>
158. *******************************************************************
162. <?php
164. The following sktest () are not called because they are "shorted" by the operator.
166. $a = (false && sktest ());
168. $b = (true | | | sktest ());
170. $c = (False and sktest ());
172. $d = (True or sktest ());
176. "| |" has a higher priority than "or"
178. $e = False | | True //$e is assigned (false | | true) and the result is true
180. $f = False or true; //$f is assigned false [Altair NOTE: ' = ' has a higher precedence than ' or ']
182. Var_dump ($e, $f);
186. "&&" has a higher priority than "and"
188. $g = True && false; //$g assigned value (True && false), False
190. $h = True and false; //$h is assigned true [Altair Note: ' = ' has a higher priority than ' and ']
192. Var_dump ($g, $h);
196. ?>

Expression A $ A && $b, expression two $ A & $b

1, the same point: two expressions are when $ A, $b are true, the expression is true. The two operators have no effect on the result of this expression.

2, different points: the expression of $ A && $b && before the $ A is false, determined that the expression is false, the logical operator && after the $b is no longer evaluated, that is, the so-called operator "short circuit". And for the expression $ A & $b, regardless of the & before the true and false, the expression after the $b still to be calculated. Whether the $b after the logical operator is run may affect subsequent data and program results.

For logical operators | | and |, the similarities and differences ibid.

The similarities and differences between & and && in PHP logic operators