{"id":699,"date":"2012-11-26T09:47:03","date_gmt":"2012-11-26T08:47:03","guid":{"rendered":"https:\/\/d-mueller.de\/blog\/?p=699"},"modified":"2016-01-11T23:28:55","modified_gmt":"2016-01-11T22:28:55","slug":"php-wtf-10","status":"publish","type":"post","link":"https:\/\/d-mueller.de\/blog\/php-wtf-10\/","title":{"rendered":"PHP WTF #10"},"content":{"rendered":"

Vorsicht! Microtime liefert negative Ergebnisse!<\/p>\n

\r\n<?php\r\n  $start = microtime();\r\n  $i = 1000;\r\n  \r\n  while ($i--)\r\n  {\r\n\t\/\/do stuff\r\n  }\r\n  \r\n  $end = microtime();\r\n\r\n  echo 'Took ' . $end - $start . ' seconds';\r\n<\/pre>\n
\"Microtime\"<\/a>
Microtime<\/p><\/div>\n
Okay, durchatmen. Wo liegt der Fehler? Kenner bemerken vielleicht, dass das W\u00f6rtchen Took<\/i> abhanden gekommen ist. Es geht einfach beim konkatenieren was schief:<\/p>\n
\r\n<?php\r\necho "Calculating " . 6 + 5 . " is fun!";\r\n<\/pre>\n
\"Konkatenation\"<\/a>
Konkatenation<\/p><\/div>\n
Nach Operator-Wertigkeit<\/a> m\u00fcssen wir nat\u00fcrlich klammern:<\/p>\n
\r\n<?php\r\necho "Calculating " . (6 + 5) . " is fun!";\r\n<\/pre>\n
\nSelbiges Problem tritt auch im Beispiel oben auf. Der Output von microtime()<\/a> ist Millisekunden (Scriptlaufzeit) Sekunden (time())<\/i>, also etwa 0.77571900 1350824124<\/b>. Da bei unserer Rechnung einfach ein String -> Float – Cast vorgenommen wird und zudem noch die Operatoren-Wertigkeit missachtet wurde, kam es zu diesem merkw\u00fcrdigen Ergebnis.<\/p>\n","protected":false},"excerpt":{"rendered":"
Vorsicht! Microtime liefert negative Ergebnisse! <?php $start = microtime(); $i = 1000; while ($i–) { \/\/do stuff } $end = microtime(); echo 'Took ' . $end – $start . ' seconds'; Okay, durchatmen. Wo liegt der Fehler? Kenner bemerken vielleicht, … Weiterlesen →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4,14,3],"tags":[],"class_list":["post-699","post","type-post","status-publish","format-standard","hentry","category-php","category-php-wtf","category-webdev"],"_links":{"self":[{"href":"https:\/\/d-mueller.de\/blog\/wp-json\/wp\/v2\/posts\/699","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/d-mueller.de\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/d-mueller.de\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/d-mueller.de\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/d-mueller.de\/blog\/wp-json\/wp\/v2\/comments?post=699"}],"version-history":[{"count":0,"href":"https:\/\/d-mueller.de\/blog\/wp-json\/wp\/v2\/posts\/699\/revisions"}],"wp:attachment":[{"href":"https:\/\/d-mueller.de\/blog\/wp-json\/wp\/v2\/media?parent=699"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/d-mueller.de\/blog\/wp-json\/wp\/v2\/categories?post=699"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/d-mueller.de\/blog\/wp-json\/wp\/v2\/tags?post=699"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}