php用正则匹配出图片img标签中的src路径，兼容
用php抓图片是个常用的需求，下面提供一个比较兼容的正则表达式来实现php抓取出页面、字符串中所有图片的src。
下面是一个范例，能匹配各种标签格式写法的图片，不管src在什么地方，还是单引号、双引号、没引号，都能匹配出来。
范例源码参考：
<?php
header("Content-type:text/html;charset=utf-8");
$str = '
<li><a href="https://www.mzitu.com/169017" target="_blank"><img src='https://i.meizitu.net/thumbs/2019/02/169017_10d01_236.jpg' alt='肉感美女刘钰儿性感图片，丰满成熟女人味十足' width='236' height='354' /></a><span><a href="https://www.mzitu.com/169017" target="_blank">肉感美女刘钰儿性感图片，丰满成熟女人味十足</a></span><span class="time">2019-02-14</span></li>
<li><a href="https://www.mzitu.com/165947" target="_blank"><img src='https://i.meizitu.net/thumbs/2019/01/165947_30c18_236.jpg' alt='勒得太紧身材毕露！宅男杀手刘钰儿火辣曲线看点十足' width='236' height='354' /></a><span><a href="https://www.mzitu.com/165947" target="_blank">勒得太紧身材毕露！宅男杀手刘钰儿火辣曲线看点十足</a></span><span class="time">2019-01-09</span></li>
<li><a href="https://www.mzitu.com/164510" target="_blank"><img src='https://i.meizitu.net/thumbs/2019/01/164510_25a23_236.jpg' alt='性感美女刘钰儿情趣睡衣私房福利 爆乳图片诱惑十足' width='236' height='354' /></a><span><a href="https://www.mzitu.com/164510" target="_blank">性感美女刘钰儿情趣睡衣私房福利 爆乳图片诱惑十足</a></span><span class="time">2019-01-04</span></li>
<li><a href="https://www.mzitu.com/164461" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/12/164461_24b12_236.jpg' alt='红色内衣娇艳火辣 性感美女刘钰儿销魂大奶无比惹火' width='236' height='354' /></a><span><a href="https://www.mzitu.com/164461" target="_blank">红色内衣娇艳火辣 性感美女刘钰儿销魂大奶无比惹火</a></span><span class="time">2018-12-30</span></li>
<li><a href="https://www.mzitu.com/161949" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/12/161949_09f10_236.jpg' alt='性感丰润凸凹有致 黑丝少妇刘钰儿白嫩多肉很有韵味' width='236' height='354' /></a><span><a href="https://www.mzitu.com/161949" target="_blank">性感丰润凸凹有致 黑丝少妇刘钰儿白嫩多肉很有韵味</a></span><span class="time">2018-12-12</span></li>
<li><a href="https://www.mzitu.com/148963" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/09/148963_31b31_236.jpg' alt='风骚女王刘钰儿人妻诱惑福利 性感露骨让你鼻血直流' width='236' height='354' /></a><span><a href="https://www.mzitu.com/148963" target="_blank">风骚女王刘钰儿人妻诱惑福利 性感露骨让你鼻血直流</a></span><span class="time">2018-09-03</span></li>
<li><a href="https://www.mzitu.com/147966" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/08/147966_24c05_236.jpg' alt='竹林诱惑！性感妹子刘钰儿翘臀美乳让人脸红心跳' width='236' height='354' /></a><span><a href="https://www.mzitu.com/147966" target="_blank">竹林诱惑！性感妹子刘钰儿翘臀美乳让人脸红心跳</a></span><span class="time">2018-08-25</span></li>
<li><a href="https://www.mzitu.com/145997" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/08/145997_07a07_236.jpg' alt='绝色美妇刘钰儿古装魅惑 血滴子肚兜释放妩媚韵味' width='236' height='354' /></a><span><a href="https://www.mzitu.com/145997" target="_blank">绝色美妇刘钰儿古装魅惑 血滴子肚兜释放妩媚韵味</a></span><span class="time">2018-08-09</span></li>
<li><a href="https://www.mzitu.com/144037" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/07/144037_25c22_236.jpg' alt='吸精女王刘钰儿直播泡温泉 香艳画面让人大饱眼福!' width='236' height='354' /></a><span><a href="https://www.mzitu.com/144037" target="_blank">吸精女王刘钰儿直播泡温泉 香艳画面让人大饱眼福!</a></span><span class="time">2018-07-27</span></li>
<li><a href="https://www.mzitu.com/142649" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/07/142649_13e11_236.jpg' alt='麻辣空姐刘钰儿制服诱惑 紧身皮衣让人鼻血狂飙' width='236' height='354' /></a><span><a href="https://www.mzitu.com/142649" target="_blank">麻辣空姐刘钰儿制服诱惑 紧身皮衣让人鼻血狂飙</a></span><span class="time">2018-07-14</span></li>
<li><a href="https://www.mzitu.com/141253" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/07/141253_02c44_236.jpg' alt='女神刘钰儿黑丝魅惑写真 硕大美胸波涛汹涌' width='236' height='354' /></a><span><a href="https://www.mzitu.com/141253" target="_blank">女神刘钰儿黑丝魅惑写真 硕大美胸波涛汹涌</a></span><span class="time">2018-07-05</span></li>
<li><a href="https://www.mzitu.com/139218" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/06/139218_17b08_236.jpg' alt='丰腴肉体的盛宴 极品尤物刘钰儿血滴子内衣叫人神魂颠倒' width='236' height='354' /></a><span><a href="https://www.mzitu.com/139218" target="_blank">丰腴肉体的盛宴 极品尤物刘钰儿血滴子内衣叫人神魂颠倒</a></span><span class="time">2018-06-18</span></li>
<li><a href="https://www.mzitu.com/137224" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/06/137224_03a41_236.jpg' alt='泡温泉当然要脱光 女神刘钰儿带你回归大自然' width='236' height='354' /></a><span><a href="https://www.mzitu.com/137224" target="_blank">泡温泉当然要脱光 女神刘钰儿带你回归大自然</a></span><span class="time">2018-06-04</span></li>
<li><a href="https://www.mzitu.com/133857" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/05/133857_10c38_236.jpg' alt='巨乳宝贝刘钰儿告诉你什么才是真正的性感' width='236' height='354' /></a><span><a href="https://www.mzitu.com/133857" target="_blank">巨乳宝贝刘钰儿告诉你什么才是真正的性感</a></span><span class="time">2018-05-10</span></li>
<li><a href="https://www.mzitu.com/133688" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/05/133688_08b22_236.jpg' alt='性感尤物刘钰儿大胆空姐制服无惧走光' width='236' height='354' /></a><span><a href="https://www.mzitu.com/133688" target="_blank">性感尤物刘钰儿大胆空姐制服无惧走光</a></span><span class="time">2018-05-08</span></li>
<li><a href="https://www.mzitu.com/132598" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/05/132598_02b39_236.jpg' alt='销魂女仆刘钰儿娇躯湿身点燃你欲望' width='236' height='354' /></a><span><a href="https://www.mzitu.com/132598" target="_blank">销魂女仆刘钰儿娇躯湿身点燃你欲望</a></span><span class="time">2018-05-02</span></li>
<li><a href="https://www.mzitu.com/131151" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/04/131151_23a31_236.jpg' alt='床上尤物刘钰儿暧昧曲线让人沉沦' width='236' height='354' /></a><span><a href="https://www.mzitu.com/131151" target="_blank">床上尤物刘钰儿暧昧曲线让人沉沦</a></span><span class="time">2018-04-22</span></li>
<li><a href="https://www.mzitu.com/128658" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/04/128658_07c12_236.jpg' alt='少妇刘钰儿太丰满了，傲人胸围遮不住' width='236' height='354' /></a><span><a href="https://www.mzitu.com/128658" target="_blank">少妇刘钰儿太丰满了，傲人胸围遮不住</a></span><span class="time">2018-04-07</span></li>
<li><a href="https://www.mzitu.com/125615" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/03/125615_17b38_236.jpg' alt='性感尤物刘钰儿韵味十足 女性曲线淋漓尽致' width='236' height='354' /></a><span><a href="https://www.mzitu.com/125615" target="_blank">性感尤物刘钰儿韵味十足 女性曲线淋漓尽致</a></span><span class="time">2018-03-17</span></li>
<li><a href="https://www.mzitu.com/123444" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/03/123444_04c16_236.jpg' alt='注意身体！乖巧女仆刘钰儿贴心为您服务' width='236' height='354' /></a><span><a href="https://www.mzitu.com/123444" target="_blank">注意身体！乖巧女仆刘钰儿贴心为您服务</a></span><span class="time">2018-03-04</span></li>
<li><a href="https://www.mzitu.com/115784" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/01/115784_12c47_236.jpg' alt='巨乳熟女刘钰儿 真正的诱惑是让你想象力爆棚' width='236' height='354' /></a><span><a href="https://www.mzitu.com/115784" target="_blank">巨乳熟女刘钰儿 真正的诱惑是让你想象力爆棚</a></span><span class="time">2018-01-12</span></li>
<li><a href="https://www.mzitu.com/114805" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/01/114805_04c17_236.jpg' alt='全是尤物,不可错过！秀人网尤蜜荟2017年度女神精选' width='236' height='354' /></a><span><a href="https://www.mzitu.com/114805" target="_blank">全是尤物,不可错过！秀人网尤蜜荟2017年度女神精选</a></span><span class="time">2018-01-04</span></li>
<li><a href="https://www.mzitu.com/112970" target="_blank"><img src='https://i.meizitu.net/thumbs/2017/12/112970_20b16_236.jpg' alt='想入非非！性感女神刘钰儿诱人曲线妙不可言' width='236' height='354' /></a><span><a href="https://www.mzitu.com/112970" target="_blank">想入非非！性感女神刘钰儿诱人曲线妙不可言</a></span><span class="time">2017-12-20</span></li>
';
$preg = '/<img.*?src=[\"|\']?(.*?)[\"|\']?\s.*?>/i';
preg_match_all($preg, $str, $imgArr);
print_r($imgArr);
?>
用php抓图片是个常用的需求，下面提供一个比较兼容的正则表达式来实现php抓取出页面、字符串中所有图片的src。
下面是一个范例，能匹配各种标签格式写法的图片，不管src在什么地方，还是单引号、双引号、没引号，都能匹配出来。
范例源码参考：
<?php
header("Content-type:text/html;charset=utf-8");
$str = '
<li><a href="https://www.mzitu.com/169017" target="_blank"><img src='https://i.meizitu.net/thumbs/2019/02/169017_10d01_236.jpg' alt='肉感美女刘钰儿性感图片，丰满成熟女人味十足' width='236' height='354' /></a><span><a href="https://www.mzitu.com/169017" target="_blank">肉感美女刘钰儿性感图片，丰满成熟女人味十足</a></span><span class="time">2019-02-14</span></li>
<li><a href="https://www.mzitu.com/165947" target="_blank"><img src='https://i.meizitu.net/thumbs/2019/01/165947_30c18_236.jpg' alt='勒得太紧身材毕露！宅男杀手刘钰儿火辣曲线看点十足' width='236' height='354' /></a><span><a href="https://www.mzitu.com/165947" target="_blank">勒得太紧身材毕露！宅男杀手刘钰儿火辣曲线看点十足</a></span><span class="time">2019-01-09</span></li>
<li><a href="https://www.mzitu.com/164510" target="_blank"><img src='https://i.meizitu.net/thumbs/2019/01/164510_25a23_236.jpg' alt='性感美女刘钰儿情趣睡衣私房福利 爆乳图片诱惑十足' width='236' height='354' /></a><span><a href="https://www.mzitu.com/164510" target="_blank">性感美女刘钰儿情趣睡衣私房福利 爆乳图片诱惑十足</a></span><span class="time">2019-01-04</span></li>
<li><a href="https://www.mzitu.com/164461" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/12/164461_24b12_236.jpg' alt='红色内衣娇艳火辣 性感美女刘钰儿销魂大奶无比惹火' width='236' height='354' /></a><span><a href="https://www.mzitu.com/164461" target="_blank">红色内衣娇艳火辣 性感美女刘钰儿销魂大奶无比惹火</a></span><span class="time">2018-12-30</span></li>
<li><a href="https://www.mzitu.com/161949" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/12/161949_09f10_236.jpg' alt='性感丰润凸凹有致 黑丝少妇刘钰儿白嫩多肉很有韵味' width='236' height='354' /></a><span><a href="https://www.mzitu.com/161949" target="_blank">性感丰润凸凹有致 黑丝少妇刘钰儿白嫩多肉很有韵味</a></span><span class="time">2018-12-12</span></li>
<li><a href="https://www.mzitu.com/148963" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/09/148963_31b31_236.jpg' alt='风骚女王刘钰儿人妻诱惑福利 性感露骨让你鼻血直流' width='236' height='354' /></a><span><a href="https://www.mzitu.com/148963" target="_blank">风骚女王刘钰儿人妻诱惑福利 性感露骨让你鼻血直流</a></span><span class="time">2018-09-03</span></li>
<li><a href="https://www.mzitu.com/147966" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/08/147966_24c05_236.jpg' alt='竹林诱惑！性感妹子刘钰儿翘臀美乳让人脸红心跳' width='236' height='354' /></a><span><a href="https://www.mzitu.com/147966" target="_blank">竹林诱惑！性感妹子刘钰儿翘臀美乳让人脸红心跳</a></span><span class="time">2018-08-25</span></li>
<li><a href="https://www.mzitu.com/145997" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/08/145997_07a07_236.jpg' alt='绝色美妇刘钰儿古装魅惑 血滴子肚兜释放妩媚韵味' width='236' height='354' /></a><span><a href="https://www.mzitu.com/145997" target="_blank">绝色美妇刘钰儿古装魅惑 血滴子肚兜释放妩媚韵味</a></span><span class="time">2018-08-09</span></li>
<li><a href="https://www.mzitu.com/144037" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/07/144037_25c22_236.jpg' alt='吸精女王刘钰儿直播泡温泉 香艳画面让人大饱眼福!' width='236' height='354' /></a><span><a href="https://www.mzitu.com/144037" target="_blank">吸精女王刘钰儿直播泡温泉 香艳画面让人大饱眼福!</a></span><span class="time">2018-07-27</span></li>
<li><a href="https://www.mzitu.com/142649" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/07/142649_13e11_236.jpg' alt='麻辣空姐刘钰儿制服诱惑 紧身皮衣让人鼻血狂飙' width='236' height='354' /></a><span><a href="https://www.mzitu.com/142649" target="_blank">麻辣空姐刘钰儿制服诱惑 紧身皮衣让人鼻血狂飙</a></span><span class="time">2018-07-14</span></li>
<li><a href="https://www.mzitu.com/141253" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/07/141253_02c44_236.jpg' alt='女神刘钰儿黑丝魅惑写真 硕大美胸波涛汹涌' width='236' height='354' /></a><span><a href="https://www.mzitu.com/141253" target="_blank">女神刘钰儿黑丝魅惑写真 硕大美胸波涛汹涌</a></span><span class="time">2018-07-05</span></li>
<li><a href="https://www.mzitu.com/139218" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/06/139218_17b08_236.jpg' alt='丰腴肉体的盛宴 极品尤物刘钰儿血滴子内衣叫人神魂颠倒' width='236' height='354' /></a><span><a href="https://www.mzitu.com/139218" target="_blank">丰腴肉体的盛宴 极品尤物刘钰儿血滴子内衣叫人神魂颠倒</a></span><span class="time">2018-06-18</span></li>
<li><a href="https://www.mzitu.com/137224" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/06/137224_03a41_236.jpg' alt='泡温泉当然要脱光 女神刘钰儿带你回归大自然' width='236' height='354' /></a><span><a href="https://www.mzitu.com/137224" target="_blank">泡温泉当然要脱光 女神刘钰儿带你回归大自然</a></span><span class="time">2018-06-04</span></li>
<li><a href="https://www.mzitu.com/133857" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/05/133857_10c38_236.jpg' alt='巨乳宝贝刘钰儿告诉你什么才是真正的性感' width='236' height='354' /></a><span><a href="https://www.mzitu.com/133857" target="_blank">巨乳宝贝刘钰儿告诉你什么才是真正的性感</a></span><span class="time">2018-05-10</span></li>
<li><a href="https://www.mzitu.com/133688" target="_blank"><img src='https://i.meizitu.net/thumbs/2018/05/133688_08b22_236.jpg' alt='性感尤物刘钰儿大胆空姐制服无惧走光' width='236' height='354' /></a><span><a href="https://www.mzitu.com/133688" target="_blank">性感尤物刘钰儿大胆空姐制服无惧走光</a></span><span class="time">2018-05-08</span></li>
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';
$preg = '/<img.*?src=[\"|\']?(.*?)[\"|\']?\s.*?>/i';
preg_match_all($preg, $str, $imgArr);
print_r($imgArr);
?>