Open the. project file inside the project to make sure that the red lines inside are correct and present, and you are successful!
<?XML version= "1.0" encoding= "UTF-8"?><projectdescription> <name>wmsadminapi</name> <Comment></Comment> <Projects> </Projects> <Buildspec> <Buildcommand> <name>Org.eclipse.wst.validation.validationbuilder</name> <arguments> </arguments> </Buildcommand> <Buildcommand> <name>Org.eclipse.dltk.core.scriptbuilder</name> <arguments> </arguments> </Buildcommand> <Buildcommand> <name>Org.eclipse.wst.common.project.facet.core.builder</name> <arguments> </arguments> </Buildcommand> </Buildspec> <Natures> <nature>org.eclipse.php.core.PHPNature</nature> <nature> Org.eclipse.wst.common.project.facet.core.nature</nature> <nature> Net.sourceforge.phpeclipse.phpnature</nature> </Natures></projectdescription>
The resource is not on the build path of a PHP project