Home > Article > Backend Development > PHP study notes 1-constants, functions
Constant: declared using const (php5), it can only be assigned once. Versions below php5 use define;
<span>1</span> <?<span>php </span><span>2</span><span>const</span> THE_VALUE = 100;<span>//</span><span>PHP5中才有const</span><span>3</span><span>echo</span><span> THE_VALUE; </span><span>4</span><span>5</span><span>define</span>('THE_VALUE',200);<span>//</span><span>低于PHP5的老版本可以使用define</span><span>6</span><span>echo</span> THE_VALUE;
Function: a code block that wraps many functions;
Advantage: easy to call elsewhere
<span> 1</span> <?<span>php </span><span> 2</span><span> 3</span><span>function</span><span> traceHelloPHP(){ </span><span> 4</span><span>echo</span> 'Hello PHP!'<span>; </span><span> 5</span><span>echo</span> '<br/>'<span>; </span><span> 6</span><span>echo</span> 'Hello World!'<span>; </span><span> 7</span><span>echo</span> '<br/>'<span>; </span><span> 8</span><span>} </span><span> 9</span><span>traceHelloPHP(); </span><span>10</span><span>11</span><span>//</span><span>函数的另外一种执行方式</span><span>12</span><span>$func</span> = 'traceHelloPHP';<span>//</span><span>把函数当成参数传递,e.g.回调方法</span><span>13</span><span>$func</span><span>(); </span><span>14</span><span>15</span><span>//</span><span>函数的传入参数--单个传入参数</span><span>16</span><span>function</span> sayHelloTo(<span>$name</span><span>){ </span><span>17</span><span>echo</span> 'Hello '.<span>$name</span>.'<br/>'<span>; </span><span>18</span><span>} </span><span>19</span> sayHelloTo('Vito'<span>); </span><span>20</span><span>21</span><span>//</span><span>函数的传入参数--多个传入参数</span><span>22</span><span>function</span> traceNum(<span>$a</span>,<span>$b</span><span>){ </span><span>23</span><span>//</span><span> echo 'a = '.$a.', b = '.$b.'<br/>';</span><span>24</span><span>echo</span> "a = <span>$a</span>,b = <span>$b</span>";<span>//</span><span>较为简便的写法</span><span>25</span><span>} </span><span>26</span> traceNum(2,3<span>); </span><span>27</span><span>28</span><span>function</span> add(<span>$a</span>,<span>$b</span><span>){ </span><span>29</span><span>return</span><span>$a</span>+<span>$b</span>;<span>//</span><span>返回值</span><span>30</span><span>} </span><span>31</span><span>echo</span> add(10,2);View Code
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